274 



RESEARCHES ON FUNGI 



is narrowed is readily understood when one remembers that it is 

 necessary for the developing cystidium to remain in connection 



with one of the rela- 

 tively small subhyme- 

 nial or tramal cells. 

 The general shape of 

 a cystidium is very 

 much like that of a 

 strut or distance-piece 

 such as one sees used 

 for preventing the 

 collapse of the sides 

 of deep trenches made 

 in the ground. The 

 narrowed end at the 

 base and the blunt 

 rounded end at the 

 apex are well suited 

 to prevent the cysti- 

 dium from being 

 pushed through the 

 hymenium of either 

 gill by gill-pressure. 



The cystidia of 

 Co'prinns atramen- 

 tarius are some of the 

 largest cells found 



Fig. 116. — C'oprinus 

 atramentarius. Cross- 

 section showing a 

 cystidium, c, stretch 

 ing across an inter- 



lamellar space, I, 

 between two gills and 

 thus se|)arating two 

 opposing hymenial sur- 

 faces. The dimorphism 

 of the basidia is [also 

 evident ; I, a long 

 basidium ; s, a short 

 basidium ; p, para- 

 physes. Magnification, 

 440. 



