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A revision of the genus Nechamandra (Hydrocharitaceae)
Aquatic Botany, 13 (1982) 505--513 Elsevier Scientific Publishing Company, Amsterdam -- Printed in The Netherlands
A REVISION OF THE GENUS NECHAMANDRA
505
(HYDROCHARITACEAE)
CHRISTOPHER D.K. COOK and RUTH LU()ND Institu t fSr Systematische BotaniC" der Universitiit Zurich, Zollikerstrasse 107, 8008 Zi~rich (Switzerland) (Accepted for publication 16 December 1981) ABSTRACT Cook, C.D.K. and LfiSnd, R., 1982. A revision of the genus Nechamandra (Hydrocharitaceae). Aquat. Bot., 13: 505--513. A taxonomic revision of the genus Nechamandra (Hydrocharitaceae) is presented with a full description, a diagnosis, typifications, synonyms, distribution maps and illustrations also including information on ecology, floral biology, anatomy, embryology, chromosome numbers, variation and taxonomic affinities. Nechamandra is considered to be monotypic. The single species~ N. alternifolia (Roxb. ex Wight) Thwaites, is considered to be native in the Indian sub-continent and introduced in Vietnam and the Sudan. The chromosome number is disputed. The taxonomic affinities of Nechamandra are with Vallisneria rather than Lagarosiphon and it is therefore transferred from the Anachariteae Ritgen. to the Vallisnerieae Endl. INTRODUCTION N e c h a m a n d r a alternifolia ( R o x b . ex Wight) T h w a i t e s is native to t h e I n d i a n s u b - c o n t i n e n t ( S u b r a m a n y a n and Balakrishnan, 1 9 6 1 ) and has established itself in the S u d a n and V i e t n a m . A l t h o u g h at the m o m e n t , n o t c o n s i d e r e d to be a n o x i o u s p l a n t it is a p o t e n t i a l l y d a n g e r o u s aquatic weed. It was felt t h a t the time was right to m a k e a t a x o n o m i c revision o f it on a w o r l d w i d e basis, This w o r k is based on a little field w o r k in India, bibliographic surveys and the s t u d y o f dried and wet-fixed p l a n t material.
TAXONOMY N E C H A M A N D R A P l a n c h o n , Ann. Sci. Nat. Bot., S@. 3, 22: 78. 1849. T y p e : Necharnandra roxburghii P l a n c h o n , norn. illeg. = N. alternifolia ( R o x b . ex Wight) Thwaites. M o n o t y p i c genus. N E C H A M A N D R A A L T E R N I F L O R A ( R o x b . ex Wight) Thwaites, E n u m . P1. Zeyl., 332. 1 8 6 4 - Vallisneria alternifolia R o x b . ex Wight in H o o k e r , Bot. Miscellany, 2(6): Suppl., 344, t. 11. ante 10 Sept. 1831, based on R o x b u r g h ross. in 0304-3770/82/0000--0000/$02.75 © 1982 Elsevier Scientific Publishing Company
506 Mus. East India Co., n. 996 -Lagarosiphon alternifolis (Roxb. ex Wight) Druce, Rep. Bot. Exch. Club Brit. Isles, 1916: 6 3 0 . 1 9 1 7 . Type: Roxburgh, Icones F1. Ind. unpublished plate n. 996 (K). --Serpicula longifolia Rottler, nom. in schaed. India, "Trankebar 1 7 9 8 " (K). --Nechamandra roxburghii Planchon, Ann. Sci. Nat. Bot., Sdr. 3, 11: 78. 1849 = Lagarosiphon roxburghii (Planchon) Bentham in Bentham & Hooker fil., Gen. PI., 3: 451. 14 April 1883, nom. illeg, based on Vallisneria alternifolia Roxb. ex Wight. Icones: Figs. 1 and 2. Hooker, Bot. Miscellany, 2(6): Suppl. t. 11. 1831. S u b r a m a n y a m K . C.S.I.R. New Delhi, Bot. Monog. 3, Aquatic Angiosperms, 150, fig. 38. 1961 (fig. 38-7 is an inaccurate representation of a female flower, the other figures are good). DESCRIPTION AND DISTRIBUTION
Formal description Dioecious, submerged perennial or annual herb. Stems: elongate, up to 1 m or perhaps longer, irregularly branched; internodes long or contracted at irregular intervals (Fig. la). Leaves: alternate, becoming clustered at irregular intervals and when clustered then usually distichous, linear, 15--60 mm long, 2--6 mm wide, green or red, sheathing and somewhat amplexicaul at base, gradually attenuate to a fine point at apex; longitudinal veins 3--7 (to 20), more or less equal, without prominent midrib (Fig. lc); cross veins very fine; margin with regularly spaced, unicellular teeth (Fig. ld). Squamulae intravaginales: usually two, at branches more, narrowly triangular to linear, up to 1 mm long, translucent~ with entire margin. Flowers: unisexual, developing within spathes. Male spathes: two (occasionally one) in leaf axils (Fig. le), of two united and conduplicate bracts, distinctly stalked with peduncles up to 2 mm long, somewhat flattened, ovoid before anthesis, becoming almost oblong in outline before dehiscence, 5--6 mm long, 4--5 mm wide, at dehiscence splitting distally with the bracts rolling back as the male flowers are released (Fig. lf); inflorescence stalk (within the spathe) transversally flattened, attenuated above, ca. 4 mm long. Male flowers: arranged in an indeterminate raceme, very numerous, densely crowded on inflorescence stalk, reaching maturity together and released underwater as obconical buds which open in air on the surface of the water. Male sepals: three, free, obovate to almost orbicular, ca. 1.5 mm long, red, reflexed and somewhat boat-like at apex. Male petal: one, obovate, ca. 1.5 mm long, white, reflexed, at apex truncate and irregularly lobed. Stamens: antisepalous, two fertile and one staminode or staminode rudimentary; filaments of fertile stamens ca. 0.5 mm long, at time of pollen transfer borne horizontally (parallel to surface of water); anthers bilocular, dehiscing distally with pollen grains remaining attached to connectives during anthesis; pollen grains inaperturate, more or less globose,
507
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Fig. 1. Necharnandra alternifolia (Roxb. ex Wight) Thwaites (a, c, d, h, Cook & Gut 34-Z; b, Wight-K; e, f, g, fixed material Ramamurthy 58156-Z). (a) Habit with female flowers at the receptive phase (scale bar: 20 ram); (b) seed (scale bar: 0.5 mm); (c) leaf (scale bar: 1 cm); (d) leaf margin (scale bar: 0.1 ram); (e) two unripe male spathes with squamulae intravaginales (scale bar: 5 ram); (f) male spathe after release of flower buds (scale bar: 2.5 mm); (g) male flower bud opened and viewed from above (scale bar: 1 mm); (h) female flower viewed from above (scale bar: 1 mm). a l m o s t s m o o t h , s o m e w h a t irregular in size, 63-~-111 p m d i a m ; s t a m i n o d e o b o v a t e , u p t o ca. 0 . 7 5 m m long, or r u d i m e n t a r y , b o r n e o p p o s i t e t h e p e t a l (Fig. l g ) . P i s t i l l o d i u m : a b s e n t . F e m a l e s p a t h e s : solitary or o c c a s i o n a l l y paired in leaf axils, o f t w o u n i t e d b r a c t s , sessile or n e a r l y so, t u b u l a r b e f o r e anthesis, b e c o m i n g o b c o n i c a l at m a t u r i t y , ca. 6 m m long; b r a c t s s e p a r a t i n g at a p e x as
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hypanthium elongates b u t remaining united below until the fruit ripens when it tears and disintegrates. Hypanthium: filiform, up to ca. 50 mm long. Female flowers: sessile~ one or rarely two in each spathe. Female sepals: three, free, widely-obovate to orbicular, spreading, ca. 1 mm long, boat-like at apex (Fig. lh). Female petals: rudimentary or absent. Staminodia: absent or rudimentary. Ovary: unilocular, of three, united carpels with parietal placentas, narrowly conical, attenuated distally into the hypanthium; stigmas three, obdeltate, as long as or exceeding the calyx, at apex irregularly lobed, adaxially papillose (Fig. lh), white or yellow at centre; fruit narrowly conical to ovoid, up to ca. 30 mm long, indehiscent; seeds numerous, ovoid but distally e l o n g a t e d ca. 1 mm long, with reticulate seed coat (Fig. l b ) .
Diagnostic features K3 C1 A2f+ls, ? K3 C0-1 G(3); leaves alternate, distichous and cauline, with 3--20 longitudinal veins but without a prominent midrib; male spathes with short, up to 2 mm long peduncles; female flowers sessile or nearly so; stigmas obdeltate and irregularly lobed at apex; seed coat distinctly reticulate.
Distribution Widespread in India south of 30°N and east of 76°E, extending eastwards to eastern Assam and central Bangla Desh and southwards to Sri Lanka. It is also found in Phuc Yen Province in northern Vietnam and in pools b y the White Nile near E1 Kawa in the Sudan (Fig. 2). In the Paris herbarium (P) one sheet of Nechamandra bears the label "CSte orientale d'Afrique; Socotra, Boivin, 1847--1852"; it is not certain if the label has been misplaced or if the species really occurs in Socotra. Although it is reported to be c o m m o n in Phuc Yen and E1 Kawa the populations are relatively small and isolated and it is highly
(a)
(b)
0 o •
Fig. 2. Distribution of N e c h a m a n d ~
•
@
•
alternifolia: (a) the Nile; (b) South Asia.
509
likely that Nechamandra is an adventive in Vietnam and the Sudan and also, perhaps, in Socotra; the native area being in eastern India.
Selected specimens India (locality uncertain: Wight (K, L)).
Uttar Pradesh: Saharanpur Distr., Indalpur, 10 October 1885, Duthie 4415 (K); Banda, Edgeworth 9004 (K).
Rajasthan: Kota, Umedgung Tank, 28 October 1970, Cook & Gut 34 (K,Z). Madhya Pradesh: Gwalior Distr., Malumpore Lake, 10 October 1980, Maries {BM); Rewa Distr., Chachai Falls, alt. 450 m, 16 August 1959, Sebastine 8812 (MH); ibid., Sebastine 8813 (MH). Maharashtra: Nagpur Distr., Bhidae Tank, alt. 250 m, 13 November 1957, Subramanyam 4554 (MH}. Madhya Pradesh: Bastar Distr., Kanker, Rajbandha Tank, alt. 500 m, 17 November 1958, Subramanyam 7142 (MH). Andhra Pradesh: Medak Distr., Narsapur, Ooracheroo Lake, alt. 713 m, 26 August 1958, Sebastine 6754 (MH); Warangal Distr., Pakhal Lake, alt. 290 m, 29 November 1960, Sebastine 11681 (MH); ibid., 25 February 1963, Henry 15906 (MH); Guntur Distr., Repalle, 13 December 1924, Narayana 16811 (MH). Tamil Nadu: Chingleput Distr., Tambaram, March 1938, Barnes 1873 (K); ibid., Vedanthangal, alt. 120 m, 21 January 1976, Henry 47059 (MH); ibid., Hanuman Nadhi, alt. 130 m, 7 December 1969, Shetty 33074 (MH); S. Arcot Distr., Kille, sea level, 12 December 1926, Raju & Nagawartha 17824 (MH); ibid., Annamalaingar, alt. 1 m, 31 January 1958, Sebastine 5212 (MH);ibid., Terukochur, alt. 150 m, 12 August 1977, Ramanurthy 51170 (MH); Thanjavur Distr., Tranquebar, 26 August & 29 December 1798, Rottler (C,K); ibid., Karikal, 1836, Perrottet 638 (G,L,P,TCD); ibid., Tiruttaraippundi, 22 August 1944, Agri. Demonstrator (MH); ibid., Thanjavur (Tanjore), December 1921, Jivanna Rao (BM); Tirunelveli (Tinnevelly) Distr., Kurumbur, 28 December 1943, Daniel (MH); ibid., Nazareth, 15 April 1930, Sundaraj & Rao (MH); Tiruchirappalli (Tricharapally) Distr., Madurai Train Halt, 17 February 1959, Subramanyam (MH); Madurai Distr., Kallandari, alt. 83 m, 23 September 1957, Subramanyam 4295 (MH); ibid., Nattam-Madurai, alt. 300 m, 30 October 1977, Chandrabose 51730 (MH); Tirunelveli (Tinnevelly) Distr., Srivaikuntam, 18 December 1943, Agri. Demonstrator (MH). Orissa: Ganjam Distr., Ganjam, December 1889, Gamble 21 706 (K). Bengal: Calcutta, Wallich 2173 (C,G); ibid., Hooker (C,K); ibid., 22 November Thomson (LE); Howrah, August 1869, Kurz (LE). Assam: Khasi, (Meghalaya), Hooker fil. & Thomson (MH); ibid., Jenkins (G,K,TCD) most collections with this label are mixed with or are Blyxa japonica (Miq.) Maxim.; Palasbari, near sea level, 10 December 1949, Koelz 24278 (L). India or Bangladesh. Bengal Or., 7 September 1850, Hooker ill. & Thomson (K,S); Lower Bengal, Dunlop (TCD); E. Bengal, bank of Nulla, 18 September 1835, Griffith {K); ibid., bank of the Nigna, 28 September 1835, Griffith (K,L,S); Wallich 5446 (BR). Bangladesh. W. Nasirabad (W. Mymensing), Ruthunguny, 18 September 1868, C.B. Clarke 7711 (K). Sri Lanka. Ceylon, Thwaites C. V. 3176 (BM, K). Nepal. Dhang, alt. 285 m, 26 October 1953, Polunin, Sykes & Williams 5881 (BM); Tansing, alt. 1000 m, 5 October 1954, Stainton, Sykes & Williams 8754 (BM).
510 Vietnam. Without locality, 1862--1866, Thorel (P); Tonkin, August 1906, Momet 419 (P); ibid., Y~n Kh~, 12 November 1882, Bon 1833 (G,P); ibid., Mao chu, 14 September 1888, Bon 394 7 (P); Phuc Yen Prov., Dong Tan, December 1935, Pdtelot 7542 (BM); ibid., Dong An, December 1935, Pdtelot 7546 (BM); ibid., Pdtelot 7551 (BM); ibid., Pdtelot 7556 (BM). Sudan. White Nile, nr. E1 Kawa, 18 December 1938, Andrews NW 89 (BM,K). Ecology The population o f N . alternifolia seen by C.D.K. Cook at Kota (Rajasthan, India) was growing in an artificial water reservoir (Umedgunj Tank) that is drained annually, usually in March and left dry for about eight weeks to kill the aquatic plants. The associated species were: Azolla pinnata R.Br., Ceratopteris thalictroides (L.) Brongn.~ Chara fibrosa Ag. em. Bruz.~ Limnophila aquatica (Roxb.) Alston, Limnophila indica (L.) Druce, Najas marina L., Nitella translucens (Pers.) Ag. em. Wood, N y m p h a e a pubescens Willd., N y m p h o i d e s hydrophylla (Lour.) O. Kuntze, Ottelia alismoides(L.) Pers., Rotala rosea (Poiret) C. D.K. Cook, Ultricularia gibba L., Utricularia inflexa Forsk. var. stellaris (L. fil.) P. Taylor. In this habitat N. alternifolia is almost certainly an annual and it is interesting that in permanent water around Kota it is largely replaced b y Vallisneria. In South India N. alternifolia is often found in permanent water where it would appear to be perennial; there are, however, no obvious perennating organs. Ghosh (1964) reports from around Calcutta that N. alternifolia forms dense populations and is c o m m o n l y found in ditches, shallow-water depressions around ricefields, choked canals and stagnant water, and that the commonest associated plants are Hydrilla, Ceratophyllum, Na]as and Nymphoides. Floral biology Ghosh (1964) reports that the male spathes are burst open by an accumulation of gas bubbles. The male flower buds are then released from 09.00 h until 17.00 h and float on the surface of the water. The male flower buds open from 11.00 h to 15.00 h with a maximum at midday. The sepals recurve lifting the stamens above the water surface. The two stamens are at first somewhat divergent and later become horizontal (Fig. 3); the pollen grains remain attached to the distal part of the filament (see Figs. l g and 3). In female plants, the flower bud breaks through the t o p of the spathe and the hypanthium stretches until the flower reaches the surface. The sepals spread b u t do not reflex and the stigma lobes arch towards the periphery. The orbicular sepals are somewhat boat-like distally and prevent wetting of the stigmas (see Figs. l h and 3). A shallow depression on the water surface, which plays an important role in the pollination o f Lagarosiphon and Vallisneria, is not seen in Nechamandra. The male flowers are released in very large numbers; they drift over the water surface and deposit pollen on the stigmas. C.D.K. C o o k has seen flowering plants at Kota, Rajasthan and agrees with Ghosh's description.
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Fig. 3. Diagrammatic representation of pollination of Nechamandra alterniflora.
Anatomy and embryology Rather little in f or m a t i on has been published on b o t h the floral and vegetative a n a t o m y o f Nechamandra. Kaul (1968, 1970) describes the structure of t h e male flower and t h e m o r p h o l o g y of t he male inflorescence. In contrast to Kaul, we observed t h a t t h e spathe ruptures somewhat irregularly usually along the midribs of the t w o bracts and often, additionally, along their sutures and no teeth were seen on t he freed edges. Adaxially t o the bases of t he t w o bracts, 4--5 squamulae-like structures were seen t hat may be interpreted as floral bracts o f th e lowermost flowers. Moreover, the vascular bundles of the flowers depart f r o m a large central bundle, which is transversally flattened. Th e d e v e l o p m e n t and structure of the female flowers was studied by Lakshmanan (1963). Contrary t o his view, we consider the male perianth to be twowhorled, consisting of t hr ee sepals and one petal. The antisepalous androecium is most p r o b ab ly made up o f t w o stamens and one, oft en minute, staminode (Fig. lg), each an t her having two groups of sporogenous tissue. No evidence was f o u n d o f vertical splitting of an original single stamen. Micro- and macrosporogenesis is dealt with by Padhye and Rao (1960), Lakshmanan (1963) and Padhye (1963). In addition to the anatomical characteristics listed b y Ancibor (1979), t he following features were observed: t h e leaves possess large secretory cells o f t e n functioning as diaphragms; t he leaf traces in th e stem are united into a central bundle and there are no peripheral bundles; air cavities in t he stem are scattered irregularly as in Blyxa and Elodea.
Chromosome numbers Sharma and B h a t t a c h a r y y a (1956), under the name Lagarosiphon roxburghii, r e p o r t e d t he following c h r o m o s o m e numbers: 2n = 9 9 , 1 0 0 , 1 0 1 . Each preparation is illustrated and an idiogramme for 2n = 100 is presented. The material was collected f r om Salt Lake (no nearer details given) and cultivated at Calcutta. The sex of the plants is n o t given and no voucher specimen has been seen. Sharma and Chatterjee (1967), under the name Nechamandra alternifolia, r e p o r t 2n = 16 and illustrate a somatic metaphase and an idiogramme, and n = 8 with normal bivalents in diakinesis and n = 8 in a meiotic metaphase I. F o t e d a r and R o y (1974) also r e p o r t e d 2n = 16, but like the previous w o r k the origin of the material and its sex is n o t given and no v o u c h e r
512 specimen has been seen. The two published idiogrammes have little in common. From microtome sections of developing male flowers (material from India, Tamil Nadu, Thanjavur collected by R a m a m u r t h y 58156) it appears that the c o u n t of 2n = 16 is probably correct. However, Sarkar et al. (1980) report 2n = ca. 100 from West Bengal.
Variation The range of morphological variation is more or less even throughout the area of distribution except that collections from northern Vietnam are very constant in form with somewhat narrow leaves. It is likely that Nechamandra is introduced in Vietnam and the populations may be genetically depauperate and/or confined within relatively narrow ecological boundaries. Unlike many dioecious Hydrocharitaceae both sexes are found t h r o u g h o u t the normal range of distribution and the seed-set seems to be fairly efficient. Within a particular population the male plants are usually somewhat larger and robuster than the females. However, when the overall phenotypic variability is considered it is not possible to distinguish male from female plants on vegetative characteristics.
Taxonomic affinities Nechamandra has always been considered to be closely related to or occasionally even congeneric with Lagarosiphon (Subramanyan and Balakrishan, 1962) and is thus placed in the tribe Anachariteae of the subfamily Hydrocharitoideae. It is difficult to see why this has never been disputed because Nechamandra is clearly more similar to Vallisneria than to Lagarosiphon. The genus Nechamandra should be transferred from the Anachariteae to the Vallisnerieae. The genera Nechamandra and Vallisneria are so similar that one could, on biological grounds, unite the two genera. However, it is felt that for the sake of nomenclatural stability it is better to retain Nechamandra as a genus. The important diagnostic features for Nechamandra in comparison to Vallisneria are: female spathe sessile or very nearly so, h y p a n t h i u m filiform, mature fruit narrowly conical to ovoid, and stamens borne horizontally. Notes Although not recorded as a serious weed Chaudhuri et al. (1976) reported that Nechamandra is eaten by larger individuals of Ctenopharyngodon idella Val. (Chinese grass carp). ACKNOWLEDGEMENTS We would like to thank the curators of the following herbaria for .allowing us to examine their material: British Museum, L o n d o n (BM); Jardin Botanique
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National, Bruxelles (BR); Royal Botanic Garden, Edinburgh (E); Conservatoire et Jardin Botaniques, Gen~ve (G); Royal Botanic Gardens, Kew (K); Rijksherbarium, Leiden (L); Komarov Institute, Leningrad (LE); Botanical Survey of India, Coimbatore (MH); Museum National d'Histoire Naturelle, Paris (P); Trinity College, Dublin (TCD); University, Ziirich (Z); Eidg. Technische Hochschule, Zfirich (ZT). We would like to thank the Fonds National Suisse de la Recherche Scientifique (No. 3.314.78) for a post doctoral fellowship for Ruth Lii6nd and the International Hydrological Decade (UNESCO) for financial support for field-work. Thanks are also due to Mr. Ramamurthy (Coimbatore) for sending fixed material and Katy Papadopoulos for typing and secretarial work.
REFERENCES Ancibor, E., 1979. Systematic anatomy of vegetative organs of the Hydrocharitaceae. Bot. J. Linn. Soc. London, 7 8 : 2 3 7 - - 2 6 6 (microfiche 1). Chaudhuri, H., Murthy, D.S., Dey, R.K. and Reddy, P.V.G.K., 1976. Role of Chinese grass carp Ctenopharyngodon idella (Val.) in biological control of noxious aquatic weeds in India: a review. In: C.K. Varshney and J. Rz6ska (Editors), Aquatic Weeds in S.E. Asia. Junk, The Hague, pp., 315--322. Fotedar, J.L. and Roy, S.K., 1974. Biosystematics of some Indian Hydrocharitaceae. In: P. Kachroo (Editor), Adv. Front. Cytogenet., pp. 357--364. Ghosh, M.K., 1964. Observations on the pollination in Nechamandra alternifolia (Roxb.) Thw. Bull. Bot. Survey India, 6: 185--187. Kaul, R.B., 1968. Floral morphology and phylogeny in the Hydrocharitaceae. Phytomorph., 18: 13--35. Kaul, R.B., 1970. Evolution and adaptation in inflorescences in the Hydrocharitaceae. Am. J. Bot., 57: 798--815. Lakshmanan, K.K., 1960. Embryological studies in the Hydrocharitaceae. Thesis of University of Madras, India, (not seen). Lakshmanan, K.K., 1963. Embryologic studies in the Hydrocharitaceae. III. Nechamandra alternifolia (Roxb.) Thw. Phyton (Argentina), 20: 49--58. Padhye, M.D., 1962. Fertilization and seed development in Nechamandra alternifolia. Bull. Bot. Coll. Sci. Nagpur, 3: 92--100. Padhye, M.D., 1963. Contribution to the embryology of Nechamandra alternifolia (Roxb.) Thw. Bull. Bot. Soc. Coll. Sci. Nagpur, 4: 39--44. Padhye, M.D. and Rao, Haripriya, 1960. Contribution to the embryology of Lagarosiphon roxburghii Benth. Proc. Indian Sci. Congr. (Bombay), 47 (3): 356--357. Sarkar, A.K., Datta, N. and Chatterjee, U., 1980. Chromosome number reports LXVII. Taxon, 29: 360. Sharma, A.K. and Bhattacharyya, B., 1956. A study of the cytology of four members of the Hydrocharitaceae as an aid to trace the lines of evolution. Phyton (Argentina), 6: 121--132. Sharma, A.K. and Chatterjee, T., 1967. C y t o t a x o n o m y of Helobiae with special reference to the mode of evolution. Cytologia, 32 : 286--307. Subramanyan, K. and Balakrishnan, N.P., 1961. The genus Nechamandra in India. Bull. Bot. Survey India, 3: 23--24. Subramanyan, K. and Balakrishnan, N.P., 1962. Is it Lagarosiphon or Nechamandra? Proc. Indian Sci. Congr., 4 9 : 3 2 4 (part III).
A REVISION OF THE GENUS NECHAMANDRA
505
(HYDROCHARITACEAE)
CHRISTOPHER D.K. COOK and RUTH LU()ND Institu t fSr Systematische BotaniC" der Universitiit Zurich, Zollikerstrasse 107, 8008 Zi~rich (Switzerland) (Accepted for publication 16 December 1981) ABSTRACT Cook, C.D.K. and LfiSnd, R., 1982. A revision of the genus Nechamandra (Hydrocharitaceae). Aquat. Bot., 13: 505--513. A taxonomic revision of the genus Nechamandra (Hydrocharitaceae) is presented with a full description, a diagnosis, typifications, synonyms, distribution maps and illustrations also including information on ecology, floral biology, anatomy, embryology, chromosome numbers, variation and taxonomic affinities. Nechamandra is considered to be monotypic. The single species~ N. alternifolia (Roxb. ex Wight) Thwaites, is considered to be native in the Indian sub-continent and introduced in Vietnam and the Sudan. The chromosome number is disputed. The taxonomic affinities of Nechamandra are with Vallisneria rather than Lagarosiphon and it is therefore transferred from the Anachariteae Ritgen. to the Vallisnerieae Endl. INTRODUCTION N e c h a m a n d r a alternifolia ( R o x b . ex Wight) T h w a i t e s is native to t h e I n d i a n s u b - c o n t i n e n t ( S u b r a m a n y a n and Balakrishnan, 1 9 6 1 ) and has established itself in the S u d a n and V i e t n a m . A l t h o u g h at the m o m e n t , n o t c o n s i d e r e d to be a n o x i o u s p l a n t it is a p o t e n t i a l l y d a n g e r o u s aquatic weed. It was felt t h a t the time was right to m a k e a t a x o n o m i c revision o f it on a w o r l d w i d e basis, This w o r k is based on a little field w o r k in India, bibliographic surveys and the s t u d y o f dried and wet-fixed p l a n t material.
TAXONOMY N E C H A M A N D R A P l a n c h o n , Ann. Sci. Nat. Bot., S@. 3, 22: 78. 1849. T y p e : Necharnandra roxburghii P l a n c h o n , norn. illeg. = N. alternifolia ( R o x b . ex Wight) Thwaites. M o n o t y p i c genus. N E C H A M A N D R A A L T E R N I F L O R A ( R o x b . ex Wight) Thwaites, E n u m . P1. Zeyl., 332. 1 8 6 4 - Vallisneria alternifolia R o x b . ex Wight in H o o k e r , Bot. Miscellany, 2(6): Suppl., 344, t. 11. ante 10 Sept. 1831, based on R o x b u r g h ross. in 0304-3770/82/0000--0000/$02.75 © 1982 Elsevier Scientific Publishing Company
506 Mus. East India Co., n. 996 -Lagarosiphon alternifolis (Roxb. ex Wight) Druce, Rep. Bot. Exch. Club Brit. Isles, 1916: 6 3 0 . 1 9 1 7 . Type: Roxburgh, Icones F1. Ind. unpublished plate n. 996 (K). --Serpicula longifolia Rottler, nom. in schaed. India, "Trankebar 1 7 9 8 " (K). --Nechamandra roxburghii Planchon, Ann. Sci. Nat. Bot., Sdr. 3, 11: 78. 1849 = Lagarosiphon roxburghii (Planchon) Bentham in Bentham & Hooker fil., Gen. PI., 3: 451. 14 April 1883, nom. illeg, based on Vallisneria alternifolia Roxb. ex Wight. Icones: Figs. 1 and 2. Hooker, Bot. Miscellany, 2(6): Suppl. t. 11. 1831. S u b r a m a n y a m K . C.S.I.R. New Delhi, Bot. Monog. 3, Aquatic Angiosperms, 150, fig. 38. 1961 (fig. 38-7 is an inaccurate representation of a female flower, the other figures are good). DESCRIPTION AND DISTRIBUTION
Formal description Dioecious, submerged perennial or annual herb. Stems: elongate, up to 1 m or perhaps longer, irregularly branched; internodes long or contracted at irregular intervals (Fig. la). Leaves: alternate, becoming clustered at irregular intervals and when clustered then usually distichous, linear, 15--60 mm long, 2--6 mm wide, green or red, sheathing and somewhat amplexicaul at base, gradually attenuate to a fine point at apex; longitudinal veins 3--7 (to 20), more or less equal, without prominent midrib (Fig. lc); cross veins very fine; margin with regularly spaced, unicellular teeth (Fig. ld). Squamulae intravaginales: usually two, at branches more, narrowly triangular to linear, up to 1 mm long, translucent~ with entire margin. Flowers: unisexual, developing within spathes. Male spathes: two (occasionally one) in leaf axils (Fig. le), of two united and conduplicate bracts, distinctly stalked with peduncles up to 2 mm long, somewhat flattened, ovoid before anthesis, becoming almost oblong in outline before dehiscence, 5--6 mm long, 4--5 mm wide, at dehiscence splitting distally with the bracts rolling back as the male flowers are released (Fig. lf); inflorescence stalk (within the spathe) transversally flattened, attenuated above, ca. 4 mm long. Male flowers: arranged in an indeterminate raceme, very numerous, densely crowded on inflorescence stalk, reaching maturity together and released underwater as obconical buds which open in air on the surface of the water. Male sepals: three, free, obovate to almost orbicular, ca. 1.5 mm long, red, reflexed and somewhat boat-like at apex. Male petal: one, obovate, ca. 1.5 mm long, white, reflexed, at apex truncate and irregularly lobed. Stamens: antisepalous, two fertile and one staminode or staminode rudimentary; filaments of fertile stamens ca. 0.5 mm long, at time of pollen transfer borne horizontally (parallel to surface of water); anthers bilocular, dehiscing distally with pollen grains remaining attached to connectives during anthesis; pollen grains inaperturate, more or less globose,
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Fig. 1. Necharnandra alternifolia (Roxb. ex Wight) Thwaites (a, c, d, h, Cook & Gut 34-Z; b, Wight-K; e, f, g, fixed material Ramamurthy 58156-Z). (a) Habit with female flowers at the receptive phase (scale bar: 20 ram); (b) seed (scale bar: 0.5 mm); (c) leaf (scale bar: 1 cm); (d) leaf margin (scale bar: 0.1 ram); (e) two unripe male spathes with squamulae intravaginales (scale bar: 5 ram); (f) male spathe after release of flower buds (scale bar: 2.5 mm); (g) male flower bud opened and viewed from above (scale bar: 1 mm); (h) female flower viewed from above (scale bar: 1 mm). a l m o s t s m o o t h , s o m e w h a t irregular in size, 63-~-111 p m d i a m ; s t a m i n o d e o b o v a t e , u p t o ca. 0 . 7 5 m m long, or r u d i m e n t a r y , b o r n e o p p o s i t e t h e p e t a l (Fig. l g ) . P i s t i l l o d i u m : a b s e n t . F e m a l e s p a t h e s : solitary or o c c a s i o n a l l y paired in leaf axils, o f t w o u n i t e d b r a c t s , sessile or n e a r l y so, t u b u l a r b e f o r e anthesis, b e c o m i n g o b c o n i c a l at m a t u r i t y , ca. 6 m m long; b r a c t s s e p a r a t i n g at a p e x as
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hypanthium elongates b u t remaining united below until the fruit ripens when it tears and disintegrates. Hypanthium: filiform, up to ca. 50 mm long. Female flowers: sessile~ one or rarely two in each spathe. Female sepals: three, free, widely-obovate to orbicular, spreading, ca. 1 mm long, boat-like at apex (Fig. lh). Female petals: rudimentary or absent. Staminodia: absent or rudimentary. Ovary: unilocular, of three, united carpels with parietal placentas, narrowly conical, attenuated distally into the hypanthium; stigmas three, obdeltate, as long as or exceeding the calyx, at apex irregularly lobed, adaxially papillose (Fig. lh), white or yellow at centre; fruit narrowly conical to ovoid, up to ca. 30 mm long, indehiscent; seeds numerous, ovoid but distally e l o n g a t e d ca. 1 mm long, with reticulate seed coat (Fig. l b ) .
Diagnostic features K3 C1 A2f+ls, ? K3 C0-1 G(3); leaves alternate, distichous and cauline, with 3--20 longitudinal veins but without a prominent midrib; male spathes with short, up to 2 mm long peduncles; female flowers sessile or nearly so; stigmas obdeltate and irregularly lobed at apex; seed coat distinctly reticulate.
Distribution Widespread in India south of 30°N and east of 76°E, extending eastwards to eastern Assam and central Bangla Desh and southwards to Sri Lanka. It is also found in Phuc Yen Province in northern Vietnam and in pools b y the White Nile near E1 Kawa in the Sudan (Fig. 2). In the Paris herbarium (P) one sheet of Nechamandra bears the label "CSte orientale d'Afrique; Socotra, Boivin, 1847--1852"; it is not certain if the label has been misplaced or if the species really occurs in Socotra. Although it is reported to be c o m m o n in Phuc Yen and E1 Kawa the populations are relatively small and isolated and it is highly
(a)
(b)
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Fig. 2. Distribution of N e c h a m a n d ~
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@
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alternifolia: (a) the Nile; (b) South Asia.
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likely that Nechamandra is an adventive in Vietnam and the Sudan and also, perhaps, in Socotra; the native area being in eastern India.
Selected specimens India (locality uncertain: Wight (K, L)).
Uttar Pradesh: Saharanpur Distr., Indalpur, 10 October 1885, Duthie 4415 (K); Banda, Edgeworth 9004 (K).
Rajasthan: Kota, Umedgung Tank, 28 October 1970, Cook & Gut 34 (K,Z). Madhya Pradesh: Gwalior Distr., Malumpore Lake, 10 October 1980, Maries {BM); Rewa Distr., Chachai Falls, alt. 450 m, 16 August 1959, Sebastine 8812 (MH); ibid., Sebastine 8813 (MH). Maharashtra: Nagpur Distr., Bhidae Tank, alt. 250 m, 13 November 1957, Subramanyam 4554 (MH}. Madhya Pradesh: Bastar Distr., Kanker, Rajbandha Tank, alt. 500 m, 17 November 1958, Subramanyam 7142 (MH). Andhra Pradesh: Medak Distr., Narsapur, Ooracheroo Lake, alt. 713 m, 26 August 1958, Sebastine 6754 (MH); Warangal Distr., Pakhal Lake, alt. 290 m, 29 November 1960, Sebastine 11681 (MH); ibid., 25 February 1963, Henry 15906 (MH); Guntur Distr., Repalle, 13 December 1924, Narayana 16811 (MH). Tamil Nadu: Chingleput Distr., Tambaram, March 1938, Barnes 1873 (K); ibid., Vedanthangal, alt. 120 m, 21 January 1976, Henry 47059 (MH); ibid., Hanuman Nadhi, alt. 130 m, 7 December 1969, Shetty 33074 (MH); S. Arcot Distr., Kille, sea level, 12 December 1926, Raju & Nagawartha 17824 (MH); ibid., Annamalaingar, alt. 1 m, 31 January 1958, Sebastine 5212 (MH);ibid., Terukochur, alt. 150 m, 12 August 1977, Ramanurthy 51170 (MH); Thanjavur Distr., Tranquebar, 26 August & 29 December 1798, Rottler (C,K); ibid., Karikal, 1836, Perrottet 638 (G,L,P,TCD); ibid., Tiruttaraippundi, 22 August 1944, Agri. Demonstrator (MH); ibid., Thanjavur (Tanjore), December 1921, Jivanna Rao (BM); Tirunelveli (Tinnevelly) Distr., Kurumbur, 28 December 1943, Daniel (MH); ibid., Nazareth, 15 April 1930, Sundaraj & Rao (MH); Tiruchirappalli (Tricharapally) Distr., Madurai Train Halt, 17 February 1959, Subramanyam (MH); Madurai Distr., Kallandari, alt. 83 m, 23 September 1957, Subramanyam 4295 (MH); ibid., Nattam-Madurai, alt. 300 m, 30 October 1977, Chandrabose 51730 (MH); Tirunelveli (Tinnevelly) Distr., Srivaikuntam, 18 December 1943, Agri. Demonstrator (MH). Orissa: Ganjam Distr., Ganjam, December 1889, Gamble 21 706 (K). Bengal: Calcutta, Wallich 2173 (C,G); ibid., Hooker (C,K); ibid., 22 November Thomson (LE); Howrah, August 1869, Kurz (LE). Assam: Khasi, (Meghalaya), Hooker fil. & Thomson (MH); ibid., Jenkins (G,K,TCD) most collections with this label are mixed with or are Blyxa japonica (Miq.) Maxim.; Palasbari, near sea level, 10 December 1949, Koelz 24278 (L). India or Bangladesh. Bengal Or., 7 September 1850, Hooker ill. & Thomson (K,S); Lower Bengal, Dunlop (TCD); E. Bengal, bank of Nulla, 18 September 1835, Griffith {K); ibid., bank of the Nigna, 28 September 1835, Griffith (K,L,S); Wallich 5446 (BR). Bangladesh. W. Nasirabad (W. Mymensing), Ruthunguny, 18 September 1868, C.B. Clarke 7711 (K). Sri Lanka. Ceylon, Thwaites C. V. 3176 (BM, K). Nepal. Dhang, alt. 285 m, 26 October 1953, Polunin, Sykes & Williams 5881 (BM); Tansing, alt. 1000 m, 5 October 1954, Stainton, Sykes & Williams 8754 (BM).
510 Vietnam. Without locality, 1862--1866, Thorel (P); Tonkin, August 1906, Momet 419 (P); ibid., Y~n Kh~, 12 November 1882, Bon 1833 (G,P); ibid., Mao chu, 14 September 1888, Bon 394 7 (P); Phuc Yen Prov., Dong Tan, December 1935, Pdtelot 7542 (BM); ibid., Dong An, December 1935, Pdtelot 7546 (BM); ibid., Pdtelot 7551 (BM); ibid., Pdtelot 7556 (BM). Sudan. White Nile, nr. E1 Kawa, 18 December 1938, Andrews NW 89 (BM,K). Ecology The population o f N . alternifolia seen by C.D.K. Cook at Kota (Rajasthan, India) was growing in an artificial water reservoir (Umedgunj Tank) that is drained annually, usually in March and left dry for about eight weeks to kill the aquatic plants. The associated species were: Azolla pinnata R.Br., Ceratopteris thalictroides (L.) Brongn.~ Chara fibrosa Ag. em. Bruz.~ Limnophila aquatica (Roxb.) Alston, Limnophila indica (L.) Druce, Najas marina L., Nitella translucens (Pers.) Ag. em. Wood, N y m p h a e a pubescens Willd., N y m p h o i d e s hydrophylla (Lour.) O. Kuntze, Ottelia alismoides(L.) Pers., Rotala rosea (Poiret) C. D.K. Cook, Ultricularia gibba L., Utricularia inflexa Forsk. var. stellaris (L. fil.) P. Taylor. In this habitat N. alternifolia is almost certainly an annual and it is interesting that in permanent water around Kota it is largely replaced b y Vallisneria. In South India N. alternifolia is often found in permanent water where it would appear to be perennial; there are, however, no obvious perennating organs. Ghosh (1964) reports from around Calcutta that N. alternifolia forms dense populations and is c o m m o n l y found in ditches, shallow-water depressions around ricefields, choked canals and stagnant water, and that the commonest associated plants are Hydrilla, Ceratophyllum, Na]as and Nymphoides. Floral biology Ghosh (1964) reports that the male spathes are burst open by an accumulation of gas bubbles. The male flower buds are then released from 09.00 h until 17.00 h and float on the surface of the water. The male flower buds open from 11.00 h to 15.00 h with a maximum at midday. The sepals recurve lifting the stamens above the water surface. The two stamens are at first somewhat divergent and later become horizontal (Fig. 3); the pollen grains remain attached to the distal part of the filament (see Figs. l g and 3). In female plants, the flower bud breaks through the t o p of the spathe and the hypanthium stretches until the flower reaches the surface. The sepals spread b u t do not reflex and the stigma lobes arch towards the periphery. The orbicular sepals are somewhat boat-like distally and prevent wetting of the stigmas (see Figs. l h and 3). A shallow depression on the water surface, which plays an important role in the pollination o f Lagarosiphon and Vallisneria, is not seen in Nechamandra. The male flowers are released in very large numbers; they drift over the water surface and deposit pollen on the stigmas. C.D.K. C o o k has seen flowering plants at Kota, Rajasthan and agrees with Ghosh's description.
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Fig. 3. Diagrammatic representation of pollination of Nechamandra alterniflora.
Anatomy and embryology Rather little in f or m a t i on has been published on b o t h the floral and vegetative a n a t o m y o f Nechamandra. Kaul (1968, 1970) describes the structure of t h e male flower and t h e m o r p h o l o g y of t he male inflorescence. In contrast to Kaul, we observed t h a t t h e spathe ruptures somewhat irregularly usually along the midribs of the t w o bracts and often, additionally, along their sutures and no teeth were seen on t he freed edges. Adaxially t o the bases of t he t w o bracts, 4--5 squamulae-like structures were seen t hat may be interpreted as floral bracts o f th e lowermost flowers. Moreover, the vascular bundles of the flowers depart f r o m a large central bundle, which is transversally flattened. Th e d e v e l o p m e n t and structure of the female flowers was studied by Lakshmanan (1963). Contrary t o his view, we consider the male perianth to be twowhorled, consisting of t hr ee sepals and one petal. The antisepalous androecium is most p r o b ab ly made up o f t w o stamens and one, oft en minute, staminode (Fig. lg), each an t her having two groups of sporogenous tissue. No evidence was f o u n d o f vertical splitting of an original single stamen. Micro- and macrosporogenesis is dealt with by Padhye and Rao (1960), Lakshmanan (1963) and Padhye (1963). In addition to the anatomical characteristics listed b y Ancibor (1979), t he following features were observed: t h e leaves possess large secretory cells o f t e n functioning as diaphragms; t he leaf traces in th e stem are united into a central bundle and there are no peripheral bundles; air cavities in t he stem are scattered irregularly as in Blyxa and Elodea.
Chromosome numbers Sharma and B h a t t a c h a r y y a (1956), under the name Lagarosiphon roxburghii, r e p o r t e d t he following c h r o m o s o m e numbers: 2n = 9 9 , 1 0 0 , 1 0 1 . Each preparation is illustrated and an idiogramme for 2n = 100 is presented. The material was collected f r om Salt Lake (no nearer details given) and cultivated at Calcutta. The sex of the plants is n o t given and no voucher specimen has been seen. Sharma and Chatterjee (1967), under the name Nechamandra alternifolia, r e p o r t 2n = 16 and illustrate a somatic metaphase and an idiogramme, and n = 8 with normal bivalents in diakinesis and n = 8 in a meiotic metaphase I. F o t e d a r and R o y (1974) also r e p o r t e d 2n = 16, but like the previous w o r k the origin of the material and its sex is n o t given and no v o u c h e r
512 specimen has been seen. The two published idiogrammes have little in common. From microtome sections of developing male flowers (material from India, Tamil Nadu, Thanjavur collected by R a m a m u r t h y 58156) it appears that the c o u n t of 2n = 16 is probably correct. However, Sarkar et al. (1980) report 2n = ca. 100 from West Bengal.
Variation The range of morphological variation is more or less even throughout the area of distribution except that collections from northern Vietnam are very constant in form with somewhat narrow leaves. It is likely that Nechamandra is introduced in Vietnam and the populations may be genetically depauperate and/or confined within relatively narrow ecological boundaries. Unlike many dioecious Hydrocharitaceae both sexes are found t h r o u g h o u t the normal range of distribution and the seed-set seems to be fairly efficient. Within a particular population the male plants are usually somewhat larger and robuster than the females. However, when the overall phenotypic variability is considered it is not possible to distinguish male from female plants on vegetative characteristics.
Taxonomic affinities Nechamandra has always been considered to be closely related to or occasionally even congeneric with Lagarosiphon (Subramanyan and Balakrishan, 1962) and is thus placed in the tribe Anachariteae of the subfamily Hydrocharitoideae. It is difficult to see why this has never been disputed because Nechamandra is clearly more similar to Vallisneria than to Lagarosiphon. The genus Nechamandra should be transferred from the Anachariteae to the Vallisnerieae. The genera Nechamandra and Vallisneria are so similar that one could, on biological grounds, unite the two genera. However, it is felt that for the sake of nomenclatural stability it is better to retain Nechamandra as a genus. The important diagnostic features for Nechamandra in comparison to Vallisneria are: female spathe sessile or very nearly so, h y p a n t h i u m filiform, mature fruit narrowly conical to ovoid, and stamens borne horizontally. Notes Although not recorded as a serious weed Chaudhuri et al. (1976) reported that Nechamandra is eaten by larger individuals of Ctenopharyngodon idella Val. (Chinese grass carp). ACKNOWLEDGEMENTS We would like to thank the curators of the following herbaria for .allowing us to examine their material: British Museum, L o n d o n (BM); Jardin Botanique
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National, Bruxelles (BR); Royal Botanic Garden, Edinburgh (E); Conservatoire et Jardin Botaniques, Gen~ve (G); Royal Botanic Gardens, Kew (K); Rijksherbarium, Leiden (L); Komarov Institute, Leningrad (LE); Botanical Survey of India, Coimbatore (MH); Museum National d'Histoire Naturelle, Paris (P); Trinity College, Dublin (TCD); University, Ziirich (Z); Eidg. Technische Hochschule, Zfirich (ZT). We would like to thank the Fonds National Suisse de la Recherche Scientifique (No. 3.314.78) for a post doctoral fellowship for Ruth Lii6nd and the International Hydrological Decade (UNESCO) for financial support for field-work. Thanks are also due to Mr. Ramamurthy (Coimbatore) for sending fixed material and Katy Papadopoulos for typing and secretarial work.
REFERENCES Ancibor, E., 1979. Systematic anatomy of vegetative organs of the Hydrocharitaceae. Bot. J. Linn. Soc. London, 7 8 : 2 3 7 - - 2 6 6 (microfiche 1). Chaudhuri, H., Murthy, D.S., Dey, R.K. and Reddy, P.V.G.K., 1976. Role of Chinese grass carp Ctenopharyngodon idella (Val.) in biological control of noxious aquatic weeds in India: a review. In: C.K. Varshney and J. Rz6ska (Editors), Aquatic Weeds in S.E. Asia. Junk, The Hague, pp., 315--322. Fotedar, J.L. and Roy, S.K., 1974. Biosystematics of some Indian Hydrocharitaceae. In: P. Kachroo (Editor), Adv. Front. Cytogenet., pp. 357--364. Ghosh, M.K., 1964. Observations on the pollination in Nechamandra alternifolia (Roxb.) Thw. Bull. Bot. Survey India, 6: 185--187. Kaul, R.B., 1968. Floral morphology and phylogeny in the Hydrocharitaceae. Phytomorph., 18: 13--35. Kaul, R.B., 1970. Evolution and adaptation in inflorescences in the Hydrocharitaceae. Am. J. Bot., 57: 798--815. Lakshmanan, K.K., 1960. Embryological studies in the Hydrocharitaceae. Thesis of University of Madras, India, (not seen). Lakshmanan, K.K., 1963. Embryologic studies in the Hydrocharitaceae. III. Nechamandra alternifolia (Roxb.) Thw. Phyton (Argentina), 20: 49--58. Padhye, M.D., 1962. Fertilization and seed development in Nechamandra alternifolia. Bull. Bot. Coll. Sci. Nagpur, 3: 92--100. Padhye, M.D., 1963. Contribution to the embryology of Nechamandra alternifolia (Roxb.) Thw. Bull. Bot. Soc. Coll. Sci. Nagpur, 4: 39--44. Padhye, M.D. and Rao, Haripriya, 1960. Contribution to the embryology of Lagarosiphon roxburghii Benth. Proc. Indian Sci. Congr. (Bombay), 47 (3): 356--357. Sarkar, A.K., Datta, N. and Chatterjee, U., 1980. Chromosome number reports LXVII. Taxon, 29: 360. Sharma, A.K. and Bhattacharyya, B., 1956. A study of the cytology of four members of the Hydrocharitaceae as an aid to trace the lines of evolution. Phyton (Argentina), 6: 121--132. Sharma, A.K. and Chatterjee, T., 1967. C y t o t a x o n o m y of Helobiae with special reference to the mode of evolution. Cytologia, 32 : 286--307. Subramanyan, K. and Balakrishnan, N.P., 1961. The genus Nechamandra in India. Bull. Bot. Survey India, 3: 23--24. Subramanyan, K. and Balakrishnan, N.P., 1962. Is it Lagarosiphon or Nechamandra? Proc. Indian Sci. Congr., 4 9 : 3 2 4 (part III).