Cortinarius Praestans in Britain

Vol 13 (1)

CORTINARIUS PRAESTANS in Britain John and Sheila Weir* ortinarius praestans, subgenus Phlegmacium, (the Goliath Web Cap) is among the largest British mushrooms and one of the rarest. It has features which should make it recognisable at all stages of its growth. As it emerges from the soil (Fig. 1) the dark purple-brown cap, breaking through the purple-white veil appears to sit on top of what will become a large clavate stem. From an early stage a characteristic wrinkling of the cap margin develops, reaching almost half of the radius, and the colour passes through chestnut to a lighter reddish brown (Fig. 2). In Cumbria mature cap diameters frequently exceed 20 cm, and 30 cm is known, with a stem of 15–20 cm. Velar remnants are characteristic and visible on the cap at all stages but can be washed away by heavy rain. Spores up to 17 µm in length are normal. Our single collection in 2003 (see below) gave a smooth variation from 14.5–19 x 8.5–10

µm. Purple bands on the lower part of the massive bulbous stem are not always visible. Confusion with other Cortinarius species seems unlikely, but we have seen a very mature C. praestans specimen with a clay-pink to vinaceous buff cap which had us searching briefly for a possible alternative. Breitenbach & Kränzlin (2000) draw attention to Cortinarius cumatilis var. robustus M.M. Moser which can reach 20 cm. diameter. This species has a more violaceous cap, which lacks the costate margin, and the spore length is not greater than 12 µm. The first recorded occurrence of C. praestans in Britain is somewhat confused by taxonomic and nomenclatural changes and I am indebted to Alick Henrici for some interesting detective work. Berkeley & Broome, 1854, reported Cortinarius (Phlegmacium) anfractus Fr. in woodland at King’s Cliffe, Northants, and simply stated that the species agreed exactly with a drawing trans-

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Fig. 1. Young buttons of Cortinarius praestans showing the caps emerging from the almost volvate white veil. Photograph © John Weir. *13 Parkside Drive, Arnside, Westmorland, LA5 0BU

doi:10.1016/j.fldmyc.2011.12.006

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Vol 13 12 (1) Carleton Rea published his Handbook of the Larger British Fungi in which he gives a good description under the now accepted name of C. praestans. Almost eighty years were to elapse before the next fully documented record by Dennis Nelson in 1987 at Roudsea Wood, Westmorland. Three further records, West Gloucestershire in 1989, North Somerset in 1992, when Bruce Ing saw it forming a ring under beech trees and Buckinghamshire at some date in the twentieth century are listed on the BMS Database. Roudsea Wood was declared a National Nature Reserve in 1955. At that time NNRs were regarded primarily as places for scientific research and Roudsea, unchanged perhaps for at least 3000 years, Fig. 2. Mature C. praestans showing the characteristic radial wrinkles on served as an outdoor laboratory the cap margin. Photograph © John Weir. for the Merlewood Terrestrial Ecology Centre at Grange over mitted by Fries, but that a “close white volva” Sands for some thirty years or so. It seems completely covered the cap when young, a feature surprising therefore that staff from here did not which seemed not to be “mentioned by authors” notice such a prominent fungus. So it was fitting in descriptions of C. anfractus. that Dennis Nelson rediscovered C. praestans in C. anfractus Fr. is a poorly understood species 1987. Subsequently its presence became almost often synonymised with C. infractus (or treated part of the local folklore; it was discussed widely as a variety of that species). Mordecai Cooke, and there were sugestions that it only appeared author of the classic 8-volume Illustrations of every ten or even twenty years. What is certain is British Fungi, realised that Berkeley’s material that in the 1980’s Dennis Nelson began his series did not fit the original concept of C. anfractus and of public forays at Roudsea Wood (and elsewhere) in 1883 renamed it C. berkeleyi. He published two on behalf of the National Park which continued excellent illustrations (Cooke 1881–1891), the until his death in August 2007. first, with spore drawings 15 x 9 µm, was Dennis would send people off for ten minutes initialled M.E.B. (= Berkeley) (Fig. 3), the second to collect whatever they could find before E.B. (= wife?). These are paintings by Cooke reassembling to discuss their finds, and it was on himself but loosely based on Berkeley originals. one such day in September 2000 that one forayer C. berkeleyi however is predated by Cortinarius emerged from the trees clutching several specipraestans Cordier (1870) and this becomes the mens of C. praestans. He was unable to retrace preferred name. his steps and no one recorded his name. John The next British collection known was made in Taylor who was also present was able to confirm September 1909 at ‘The Baslow Foray’ in the find. We joined a search of the area for more Derbyshire, which is reported in Trans. Brit. specimens some four days later, without success, Myc. Soc. 3 (3): 136-149 (1909). It is merely listed and Dennis gave us the material which we dried in the records of fungi seen and does not receive and sent to Kew. Spores up to 18µ were measured any special mention in the text as do all of the but at five days old they had to be from the stem new and rare species. Hence it is likely that apex. participants were familiar with it. In 1922

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Vol 13 (1) The decades immediately before and after the turn of the Millenium to some extent marked a turning point for fungal recording too. Increasing numbers of people were joining the county Fungus Groups and foraying; the Fungus 2000 initiative introduced more people to the BMS Fungal Database and Field Mycology was published. So it is perhaps not surprising that over the next decade Cortinarius praestans was recorded at Roudsea in at least 8 of the 10 years. In 2001 Pat Livermore, who was out of the Country in 1987, finally realised her ambition with a good sighting. We ourselves have been regular visitors since 2002 and so too has Pauline Greenhalgh. 2003 saw two separate single specimens one of which was the clay-pink one referred to above, which also went to Kew. In 2004 two groups appeared about 10 metres apart totalling more than 20 fruiting bodies, just in time for a large specimen (it was 30 cm across), rather past its best, to be transported to the BMS Autumn Foray in Sussex. This area was subsequently coppiced in the following winter. Most encouragingly, in 2007 a single specimen appeared at the edge of an old coppicing from which all undergrowth had now disappeared following the regrowth of the hazel canopy, and

we have seen numbers increase and spread each year until in 2011 the mycelium must have been at least 7 metres in extent. Even after depradation by molluscs, which is not insignificant, there were some five groups, plus a sixth (see Front Cover) some distance away which the terrain suggests could well have been on a different mycelium. Over this period we have occasionally found single fruitbodies in other parts of the wood with no subsequent appearances in following years. Writing this note has brought attention to the possibility that collections from Roudsea may be on average somewhat larger in both fruitbody size and spore size than is suggested in most published descriptions. This needs further investigation. Speculation about the requirements of Cortinarius praestans is just that. Calcareous Ancient Woodland is probably top of the list, and while the fungus is quite happy to form mycorrhiza with hazel alone, it has also been recorded by various authors with Quercus, Tilia, Carpinus and Fagus as well as conifers. Adequate moisture is surely essential, and in this respect we have just had four cool wet summers on the run. A violent thunderstorm at the end of August 2004 may have aided that year’s successful fruiting. But the even better show of the last four years is probably an exception rather than the rule. Many of the larger Cortinarius species in subgenus Phlegmacium fruit erratically but sometimes in considerable numbers when they do – Cortinarius praestans is probably no exception. We shall watch and see. It is listed as “Endangered / B /” in the 2nd Edition of the Red Data list and should not be collected.

References Berkeley, M. & Broome, C.E. (1854). Notices of British Fungi No. 672. Annals and Magazine of Natural History May–June: 398. Breitenbach,J. & Kränzlin,F. (2000). Fungi of Switzerland, Vol. 5. Mycologia, Luzern. Cooke, M.C. (1881–1891). Illustrations of British Fungi Vol. 5. Williams and Norgate, London.

Fig. 3. One of the two plates of Cortinarius berkeleyi in Cooke’s Illustrations of British Fungi, 1886.

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