258 RESEARCHES ON FUNGI 



which would otherwise be provided by the increase in the spore-free 

 part of the gill is constantly eliminated and the spores can escape 

 from the gills even although the gills are tilted. 



In the evolution of the Coprini from the Aequi-hymeniiferae the 

 first change was probably the change of shape of the gills from 

 wedge-shaped in cross-section to parallel-sided or subparallel-sided 

 in cross-section. This permitted of the gills becoming thinner and 

 more closely packed in the young pileus ; but it brought with it 

 the disadvantage that, even with a very precise response to the 

 stimulus of gravity, it became impossible for the gills to take up 

 such strictly vertical positions that the spores after discharge could 

 all escape freely down the interlamellar spaces without striking the 

 sides of the gills. Then, we may imagine, the gills ceased to react 

 to gravity and pari passu underwent other important changes. 

 The spores, instead of being produced and liberated from all parts 

 of the gills (every square mm.) simultaneously throughout the 

 spore-discharge period as now occurs in the Aequi-hymeniiferae, came 

 to be produced and liberated in succession from below upwards 

 on each gill. It is not difficult to suppose that the numerous 

 irregular waves of hymenial development which one can observe 

 in the mottled gills of many Aequi-hymeniiferae, e.g. Panaeolus 

 carnpanulatus, became altered in their movements so as to form 

 one grand upward-moving hymenial wave such as we now find on 

 the gill of a Coprinus. The production and liberation of spores is 

 accompanied in all Agaricineae by the emptying of the basidia and 

 paraphyses and by a diminution in the amount of protoplasm, etc., 

 in the hyphae of the subhymenium and trama. The production 

 and liberation of the spores from below upwards on each gill in 

 our evolving Coprinus therefore inevitably brought in its wake the 

 exhaustion of the gills from below upwards ; and the exhaustion of 

 the gills from below upwards was almost as inevitably followed by 

 the death of the gills from below upwards. The death of the gills 

 from below upwards resulted in the liberation of enzymes from the 

 dying cells from below upwards, and this in turn led to the auto- 

 digestion of the spore-free portions of the gills from below upwards. 

 The autodigestion of the spore-free portions of each gill from below 

 upwards ensured the progressive elimination of an obstacle which, 



