PLEUROTUS OSTREATUS 479 



continuously for a month. Berkeley ^ thus describes the fungus : 

 " Pileus soft, fleshy, subdimidiate, conchate, ascending, turning 

 pale ; stem short or obsolete, firm, elastic, strigose at the base ; 

 gills decurrent, rather distant, anastomosing behind, dirty- white." 

 And he adds : " On trees, especially laburnum. Late in the autumn 

 and winter. Pileus cinereous." Atkinson ^ states that the pileus is 

 " white, light grey, buff or dark grey, often becoming yellowish 

 on drying." The name Oyster Fungus owes its origin to the fact 

 that the form of the fruit-body sometimes suggests an Oyster shell. 



In the summer of 1923, at Sutton Park, Warwickshire, I found 

 some fully expanded fruit-bodies of Pleurotus ostreatus attached to 

 the trunk of a Holly Bush {Ilex Aquifolium). As there had been 

 no rain for about a month, the pilei were very hard and dry and the 

 gills stiff and somewhat curled. Doubtless, during their develop- 

 ment, the pilei had shed large numbers of spores. I took the 

 fruit-bodies home, kept them dry for about a month, and then 

 allowed them to absorb water through their upper surfaces. They 

 soon revived and, in the course of the next few days, gave rise to 

 copious spore-deposits. Evidently under natural conditions in the 

 open, the fruit-bodies of Pleurotus ostreatus, like those of species of 

 Lenzites, Polystictus, etc., may have their spore-discharge period 

 temporarily interrupted by drought. 



The observations about to be recorded were made by the author 

 in November and December, 1922, near Birmingham, England, 

 during a period of leave-of-absence from the University of Manitoba. 



Among the late-autumn fungi in my father's garden at King's 

 Heath the Oyster Fungus was conspicuous, for clusters of its fruit- 

 bodies appeared on several Poplars {Populus serotina) from which a 

 few years before all the main branches had been lopped off (Fig. 199, 

 p. 483). The severe trimming to which the trees had been subjected 

 had doubtless provided the conditions for the entry of the mycelium 

 into the wood. All the trees appeared to be dying and some were 

 already dead. Two of the latter had been cut down and removed 

 to a wood-shed which was open on one side. 



1 M. J. Berkeley, he. cit., pp. 135-136. 



2 G. F. Atkinson, Mushrooyns, Edible and Poisonous, etc., Ithaca, U.S.A., 1900, 

 p. 104. 



