132 The Irish Naturalist. J"ly- 



DUBLIN MICROSCOPICAL CLUB. 



May io. — The Clul) nut at Lcinstcr House. A. R. Nichols, M.A. 

 (President) in the Chair. 



Dr. G. H. Pethybridgic exhibited various stages of development of 

 the Potato " Collar Fungus," Hypochnus solani, (Prill, et Del.) In its 

 fruiting stage this fungus forms a white, felt-like covering of no great 

 density or thickness around the bases of potato stalks (it has also been 

 observed on the carrot) close to the soil and extending upwards for a 

 distance of an inch or more. This " collar " consists of much branched 

 mycelium which for the most part is colourless but is occasionally tinged 

 with brown. It bears large numbers of basidiosporcs which easily fall 

 off. but it does not penetrate into the tissues of the potato stalk, nor 

 have any haustoria or sucker-like organs been observed. In the United 

 States the fungus has (apparently unnecessarily) been given the name of 

 Corticium vas;nm var. solani, and Rolfs showed in 1904 that it is the spore- 

 bearing stage of a fungus which has been known for a much longer time 

 under the name of Rhizoctonia solani. In the Rhizoctonia condition the 

 mycelium is brown and is very frequently found on the surface of potato 

 tubers, where it also forms dense aggregations or sclerotia, which are 

 exceedingly common in some parts of Ireland. During last summer 

 confirmatory evidence of the oneness of Hypochnus and Rhizoctonia was 

 obtained at the Clifden Station for the Investigation of Plant Diseases, 

 since it was found possible to trace an unbroken connection between the 

 mycelium of the " collar " and the sclerotia on the surface of the tuber. 

 Further confirmatory evidence of the same thing was published early in 

 the present year by Riehm. The fungus, whether in its sterile sclerotial 

 condition or in the fructification or " collar " stage shoukl therefore be 

 known in future as Hypochnus solani (Prill, et Del.), and the older name 

 of Rhizoctonia solani (Kiihn) must be dropped. 



Prof. G. H. Carpenter showed the anterior spiracles of the puparium 

 of a small two-winged fly, Scaptomyza flaveola (Fallen) whose larva feeds 

 on the surface, or mines in the tissues of the leaves of crucifers. The 

 specimen exhibited had been reared from larvae feeding on the leaves of 

 Swede Turnips from Dundalk. The anterior spiracle in the puparium of 

 this insect is remarkable for the elongate branching arrangement of the 

 external air-tubes, so that it presents somewhat the appearance of a 

 stag's antler. Some details of the early stages will shortly be publi.shed 

 with illustrations, in the Journal of Economic Biology, vol. vi. 



BELFAST NATURALISTS' FIELD CLUB. 



March 15. — Geological Section. — \V. J. C. Tomlinson in the Chair. 

 William Gray delivered a lecture on '• Limestone." A discussion 

 followed, in which Robert Welch, A. R. Dwerryhouse, .\. W. Stelfox, 

 and the Chairman took part. 



May 27. — Excursion to Torr Head. — This was the inaugural ex- 

 cursion of the season, when twenty-four members and friends proceeded 

 to Ballycastle by the eight o'clock train. Upon arrival brakes were 

 immediately mounted for Torr. Many features of geological interest 

 were passed during the drive, of which the great accumulation of glacial 



