COPRINUS STERQUILINUS 247 



removed from a living fruit-body and placed flat on a glass slide 

 without any mounting fluid. A cover-glass was then laid over it. 

 As the cover-glass touched the surface of the gill only in a few places, 

 a large part of the zone of spore-discharge was left undisturbed. 

 Under these conditions, I was able to examine this zone with the 

 high power of the microscope ; and, with a magnification of 440, 

 I succeeded in observing the discharge of a considerable number of 

 spores. Sometimes, however, the under side of the cover-glass 

 became fogged owing to the condensation of water- vapour upon it ; 

 and then the preparation was spoiled. In successful preparations, 

 it was found that a drop of fluid was always excreted from the 

 hilum of each spore just before spore-discharge was consummated ; 

 and a number of such drops have been introduced in the zones of 

 spore-discharge represented in Figs. 104 and 105 (pp. 242 and 249). 

 A drop, after its first formation, continues to grow for from 15 

 to 30 seconds, and at the end of this time it has attained its 

 maximum diameter which is equal to from one-third to one-half 

 the diameter of the spore. As soon as the drop has become of full 

 size, the spore is discharged. As the spore disappears, the drop 

 disappears too, so that it can no longer be seen at the end of the 

 sterigma. Doubtless it is carried away by the spore in the manner 

 which has been described for other species.^ In a number of other 

 Hymenomycetes with smaller spores, the excreted drop grows 

 only for from 5 to 10 seconds, and then discharge takes place. 

 Coprinus sterquilinus possesses unusually large spores and corre- 

 spondingly large drops. Possibly it is on this account that the 

 growth of the drops takes the unusually long time of 15 to 30 

 seconds. 



It was sometimes observed in my preparations that, when a fruit- 

 body had been grown under conditions in which the atmosphere 

 around it was saturated with water-vapour, some or most of the 

 spores in the zone of spore-discharge failed to be shot away. Drops 

 were seen to appear in the normal manner (Fig. 106, A), and they 

 rapidly grew to the normal maximum size (B) ; but then, instead 

 of the spores being discharged, the drops continued to grow in 

 volume. They soon became so big that they stepped up from the 

 1 ThQse Researches, vol. ii, 1922, pp. 14-17. 



