486 RESEARCHES ON FUNGI 



About the middle of December, the fruit-body attained full size 

 and, on December 18, its pileus measured 7 inches across from side 

 to side and 5 inches from back to front. The blue colour of the 



Ym 201 —Pleurotus ostreatus. The under surface of a full-grown fruit-body removed 

 * from a Poplar (Populus serotina), showing the gills and the mterlamellar spaces. 

 Photographed by J. P. HiUhouse at King's Heath, Birmingham, England, on 

 December 23,1922. Natural size. 



upper surface of the pileus had now disappeared and become 

 replaced by a yellowish-brown. Moreover, the edge of the pileus, 

 which during the first few weeks of the fruit-body's development 

 had been characteristically involute (c/. Fig. 199, also Vol. I, 

 Fig. 2, p. 22), had now become flattened or even somewhat 

 turned-up (c/. Fig. 201, also Vol. I, Fig. 3, p. 23). A section 



