COPRINUS STERQUILINUS AND ITS SPORES 79 



in the drawings G-J, and the formation of septa in the drawings 

 I, J, and F. 



A cytological study of a young mycehum of Coprinus sterquilinus 



'Wm 



Fig. 49. — Coprinus sterquilinus. Fruit-bodies which came up spontaneously on 

 unsterilised horse dung sent from England. Left : a young fruit-body, which 

 originated in a dark crevice between three dung-balls, still snowy white ; 

 a white layer of mycelium covers the front part of the dung-ball. Right : a 

 small fruit-body, which originated at the base of a dung-ball ; the blackness, 

 of the pileus is due ( 1 ) to the black spores on the hymenium of each gill and 

 (2) to a dark-brown pigment in the cells of the hymenium, trama, and pileus- 

 flesh ; the blackish tint of the stipe is not due to bruising but to a dark-brown 

 pigment developed in its cells ; the pileus is expanding but has not yet begun 

 to shed any of its spores. Natural size. 



produced in the course of about 24 hours from a spore in a film of 

 dung-agar on a sHde in a moist Petri dish is represented in Fig. 52. 

 The mycelium was fixed in formalin-acetic-alcohol, was stained 

 with iron-alum haematoxylin, and was counterstained with light- 



