SPORES SWALLOWED BY HORSES 



8i 



enquire whether the spores liberated by the fruit-bodies of this 

 fungus infect the dung in fields by settling on it directly from the 

 air, or whether they first settle on the grass and are then swallowed 

 by a grazing horse so that they pass down an alimentary canal, 

 become involved in the faeces, and thus come to be embedded in 



Fig. 51. — Coprinus sterquilinus. Germination of spores in absence of bacteria. 

 Spores taken from a spore-deposit 14 months old were placed in hanging 

 drops of cleared and sterilised horse-dung agar, where they soon germi- 

 nated. The time they had been immersed in the culture medium before being 

 drawn was : A-E, G, and H, 12-5-13-5 hours ; I and J, 15 hours ; F, 17-5 

 hours. The germ-tubes and young mycelia are shown in A— F in external 

 view and in G-J in optical section. The germ-tube of each spore has been 

 emitted at the apical germ -pore. The development of vacuoles is seen in G-J. 

 There are no septa in D, E, and H, one septum in I, two in J, and five in F. 

 Drawn by A. H. R. Buller and Ruth Macrae. Magnification, 400. 



the excreta at the moment when these are extruded and deposited 

 on the ground in the form of dung-balls. It is, of course, conceivable 

 that both methods of infection take place. However, as a result 

 of experiments which will now be described, there seems no reason 

 for doubting that the actual mode of infection is always via the 

 alimentary canal of the horse. 



Experiment I. Some just-dropped horse-dung balls were ob- 

 tained from a stable. The surface of the unsterilised balls was then 

 darkened with spores by rubbing it with the gills of a large expanding 

 fruit-body from which spores were being discharged. The balls 



VOL. IV. 



