FOMES APPLANATUS 123 



applanatus into living trees results in an extensive browning of the 

 inoculated wood with a multiplication of tyloses, the browning of 

 the wood and the multiplication of the tyloses being far in excess 

 of what is caused by traumatic stimulation. 1 



Spore Structure. According to White, Fomes applanatus 

 produces basidiospores only. These spores alone, therefore, bring 

 about the dissemination of the fungus in nature. Conidia are not 

 produced by the mycelium nor, as has commonly been affirmed, by 

 the upper surface layer of the sporophore. 2 



The basidiospore-wall, according to White, is not simple but 

 double, for it consists of an outer thin hyaline layer and an inner 

 thick yellow papillate layer. White regards the whole spore as a 

 thick-walled chlamydospore formed inside the thin exterior hyaline 

 wall. 3 I have examined the spores of Fomes applanatus, as well as 

 the similar but larger spores of Ganoderma colossus, with the result 

 that my conception of the spore-wall is quite different from that 

 of White. It seems to me that each spore has one continuous, 

 rather thick wall made up of two layers : (1) an outer, very thin, 

 colourless, homogeneous layer formed whilst the spore is growing 

 from a tiny rudiment to full size, and (2) an inner and much thicker 

 layer, formed more slowly during the ripening of the spore, of a 

 whitish or yellowish colour, and marked from within outwards by 

 numerous fine yellowish-brown striae. What the nature of these 

 striae is I do not know, but I do not regard them as papillae. 

 Atkinson, 4 who first studied them and whose general conception 

 of the wall is similar to my own, looks upon them as " perforations 

 into which it appears that the brown or yellowish-brown contents 

 of the spore project." The continuity of the two layers of the 

 wall is shown by the fact that, if one takes dried spores of Fomes 

 applanatus or Ganoderma colossus and places them in glycerine, 

 no trace of air enclosed between the outer and inner wall-layers 

 can be observed. In having a thin, colourless, outer wall-layer 

 and a thick, pigmented, inner wall-layer the basidiospore of Fomes 



1 J. H. White, " On the Biology of Fomes applanatus" Trans. Roy. Canadian 

 Institute, Toronto, 1919, pp. 159-167. 



2 Ibid., p. 137. 3 Ibid., pp. 138, 167. 



4 G. F. Atkinson, " On the Identity of Polyporus ' applanatus ' of Europe 

 and North America," Annales Mycologici, vol. 6, 1908, pp. 179-191. 



