460 RESEARCHES ON FUNGI 



of the pileus-ilcsh at the upper end of the fruit-body, and the attachment 

 of the rest of the fruit-body to the tree-trunk is merely by adhesion to 

 the bark. 



Fomes igniarius develops a new layer of hy menial tubes each summer 

 and has a summer spore-discharge period of somewhat more than t\vo 

 months' duration. 



In Manitoba, owing to winter frost, the spore-discharge period of 

 Daedalea confrayosa and certain other lignicolous Hymenoniycetes is 

 often divided into two parts, one autumnal and the other vernal. 



In the Polyporeae, the pilei : (1) may be solitary as in Fomes ofli.cinali*, 

 (2) may be imbricated as in Polyporus sulphureus, or (3) may form part 

 of a compound fruit-body as in P. umbellatus. The author discusses 

 the significance of these arrangements. 



Chapter V. - Fomes applanatus is an important wood-destroying 

 fungus which attacks upwards of fifty species of trees. The author 

 treats of its biology, more especially of its production and liberation 

 of spores, in the light of the investigations made by J. H. White and 

 by himself. The basidiospore should not be regarded as a chlamydo- 

 spore. Fomes applanatus may produce 10 successive annual tube- 

 layers ; F. officinalis, 45 ; and F. igniarius, 80. 



Owing to the narrowness, length, and crowding of the hymenial 

 tubes a fruit-body of Fomes applanatus has a very large hymenial surface. 

 White found that a large fruit-body liberated about 30,000,000,000 

 spores in 24 hours and that the spore-fall period had a duration of six 

 months (the longest known). The visible emission of spore-clouds from 

 the pileus has been observed by White at Ottawa and by the author 

 at Kew. The length of the spore-fall period in the Hymenoniycetes 

 is roughly correlated with the mechanical consistence of the fruit-bodies, 

 the most watery fruit-bodies having the shortest spore-fall period, and 

 the most woody the longest. The number of spores liberated per annum 

 by a very large fruit-body of Fomes applanatus is of the same order 

 of magnitude as the number liberated from a fruit-body of the Giant 

 Puff-ball. The great length of the spore-fall period appears to be 

 correlated with the long-continued growth in length of the hymenial 

 tubes ; but a full explanation of the duration of the spore-fall period 

 can be given only after the organisation of the hymenium has been 

 elucidated in detail. 



The production of vast numbers of spores by the fruit-bodies 

 of wood-destroying fungi appears to be necessary to permit of these 

 fungi overcoming the difficulties of invading new woody substrata with 

 .sufficient frequency to maintain themselves under natural conditions. 



Chapter VI. In the Hydneae, the Tremellineae, and the Clavarieae, 

 the form of the fruit-body is intimately correlated with the size 

 and strength of the basidial guns which discharge the spores. In 

 tin- Kxobasidieae, the absence of a fruit-body is correlated with the 



