144 RESEARCHES ON FUNGI 



of the tubes all the way down, from the top to the bottom, except 

 the last 3 mm., where, apparently, growth in length was still pro- 

 ceeding. No actual sign of exhaustion of the hymenium in each 

 tube from above downwards was therefore observed ; but the 

 tubes may not have been studied late enough in the year. On the 

 other hand, it is possible that the hymenium of Fomes applanatus 

 is organised in a different manner from that of the Agaricineae 

 and that interesting discoveries in this connection may await the 

 careful investigator. 1 



The Significance of the Production of Vast Numbers of Spores. 

 As we have seen, many of the larger Hymenomycetes, e.g. Fomes 

 applanatus, Polyporus squamosus, Psalliota campestris, etc., liberate 

 many thousands of millions of spores during their spore-fall period. 

 Since the number of plants of any hymenomycetous species remains 

 fairly constant from year to year, it is clear that for every spore 

 of Fomes applanatus, Polyporus squamosus, Psalliota campestris, 

 etc., which succeeds in germinating and in establishing a nourishing 

 sporophore-producing mycelium, some thousands of millions of 

 spores must fail. This fact suggests an enquiry into the significance 

 of spore numbers. What advantage accrues to Hymenomycetes 

 from the production and liberation of vast quantities of spores most 

 of which are doomed to die either before or after germination 

 without producing a fruiting mycelium ? Is not the production 

 and liberation of spores by thousands of millions a wasteful process ? 

 We shall now attempt to answer these questions. 



Let us, in order to be concrete, consider the production of spores 

 by Fomes applanatus. This fungus, as we have seen, is a wound- 



1 In certain large, rapidly developing species of Polyporus, e.g. Polyporus 

 squamosus (vide the longitudinal spore-deposit shown in vol. i, Plate IV, Fig. 28), 

 P. hispidus (tubes up to about 20 mm. long), P. cuticvlaris (tubes 8 mm. long), 

 the hymenial tubes, when about full-grown, produce and liberate spores throughout 

 their whole length, except close to their apertures. Whether, toward the very end 

 of the spore-fall period, they show any signs of exhaustion from above downwards, 

 I have not as yet ascertained. If they do not, since hymenial tubes begin to shed 

 spores soon after they begin to grow downwards and elongate basally for a week 

 or more, it seems likely that the number of spores ultimately produced and liberated 

 by each unit of area of the hymenium in any tube must be greatest at the top of 

 the tube, must be least at the bottom, and must decrease in the tube from above 

 downwards. Further investigations alone can teach us the truth about this matter. 



