86 RESEARCHES ON FUNGI 



large pileus, the number of gills may exceed 100 ; but, in a dwarf 

 pileus, this number is greatly reduced and is usually not more, 

 and sometimes less, than 20. In a dwarf pileus, which was less 

 than 1 mm. in diameter, the gills were very shallow and only 

 numbered 9, with faint traces of some very short intermediate ones. 

 The smaller the pileus, the fewer are the cystidia projecting from 

 its gills ; and in the dwarf pileus just referred to as being less than 

 1 mm. in diameter there w T ere no cystidia at all. The largest of the 

 cells in the filaments making up the pileal scales of a dwarf fruit- 

 body are appreciably smaller than similar cells of a large pileus. 

 Finally, the spores of dwarf fruit-bodies, while of about the same 

 width as those of large fruit-bodies, are distinctly shorter. The 

 size of the cell-elements of the fruit-bodies of Coprinus lagopus 

 therefore appears to be correlated to some extent with vigour of 

 fruit-body development. 



On exhausted horse-dung balls, where the competition among 

 various fungi for food materials is very keen, the production of 

 dwarf fruit-bodies by Coprinus lagopus is quite common ; and 

 I have often met with them in fields in England. There is no diffi- 

 culty in convincing one's self that these tiny fruit-bodies from 

 1 to 10 mm. high really do belong to the species in which they have 

 been placed. The colour and hairy scales of the pileus, the nature 

 of the cystidia, the intense blackness and oval shape of the spores, 

 etc., which one observes in studying a dwarf, all point to the con- 

 clusion that the dwarf should be regarded as a product of Coprinus 

 lagopus ; but the most convincing evidence that this conclusion is 

 correct is afforded by pure cultures. I found that, when the spores 

 of a dwarf fruit-body are sown on sterilised horse dung, large fruit- 

 bodies are obtained with stipes upwards of 100 mm. in length and 

 pilei from 15 to 40 mm. in width, exactly resembling typical large 

 specimens of Coprinus lagopus. 



The dwarf fruit-bodies under consideration are of interest not 

 only to the physiologist but also to the systematic mycologist, for 

 I am convinced that very frequently, on account of their small 

 size, their true affinity has not been recognised and they have 

 therefore been placed in a species distinct from Coprinus lagopus. 

 Even Massee, who wrote a monograph on the genus Coprinus, made 



