DEVELOPMENT OF STROPHARIA EPIMYCES 



W. B. McDoUGALL 



(with ten figures) 



Stropharia epimyces (Peck) Atk. was first described by Peck 

 (9) in 1884 as Panaeolus epimyces. It was redescribed by Atkinson 

 (i) in 1902 and again in 1907 (2), and placed in the genus Stro- 

 pharia because of the purpHsh tinge of the spores and the presence 

 of an annulus. It is considered rare, but it has occurred in several 

 localities north of Urbana during each of the 4 summers I have 

 spent in Illinois, and was particularly abundant during the seasons 

 of 1915 and 1916. 



As is well known, this plant always occurs as a parasite on 

 another mushroom. The identification of the host plant was 

 first published by Atkinson (i) as Coprinus atramentarius. Later 

 a second host, C. comatus, was added by Sherman (id). All 

 specimens collected at Urbana have been on C. comatus. Several 

 photographs of Stropharia epimyces and its host were published by 

 McDouGALL (8), and excellent photographs were also published 

 by Atkinson (2). 



Material for the developmental study of this plant was obtained 

 within the city park of Urbana in Spetember 1915. It was imbed- 

 ded, sectioned, and stained with fuchsin. 



Development 



The smallest carpophore sectioned measured 0.9 mm. by 

 1.2 mm. (fig. i). In this the pileus and stem fundaments cannot 

 be said to be differentiated, but the primordium of the hymeno- 

 phore already appears as a patch of heavily stained hyphae on 

 each side of the median longitudinal section. Aside from this 

 hymenophore primordium there is no differentiation of the carpo- 

 phore at this stage, except a layer of coarse and rather loose hyphae 

 on the periphery, representing the universal veil or blematogen. 

 The size of the carpophore is not always an index of its degree of 

 Botanical Gazette, vol. 67] [258 



