88 INTRODUCTION TO THE STUDY OF FUNGI 



formed, like* starch, from the free carbon-dioxide of the atmo- 

 sphere, but out of previously existing organic carbon compounds, 

 especially the products of the decomposition of other food 

 materials. Examination of the ergot of Claviceps has shown 

 that the oily material is changed into glycogen in the same 

 manner that oily material is converted into starch in germinat- 

 ing seed. There is a special accumulation of glycogen in the 

 capitulum of the young Claviceps. 



The varnished appearance of the pilei in some of the 

 species of Fomes, such as Fomes laccatus, Fom.es australis, and 

 others, is affirmed by Dr. Wettstein to be due to a secretion of 

 resin. The special hyphae are of peculiar form, thickened 

 above clavately, and containing when young an oily yellow 

 fluid. Eventually protuberances appear at the end of the 

 hyphae, which gradually increase and exude a cap of resin. 

 These exudations flow together and form a continuous coat. 1 

 A yellow resin has been found by Zopf in Polyporus hispidus, 

 which exudes when fresh a plentiful supply of yellow juice 

 like a pigment, which stains paper of a gamboge yellow. 

 Zopf reports that there are two substances : one is the yellow 

 resin, which is insoluble in water, but otherwise resembling 

 gamboge ; the other a soluble yellowish -green pigment with 

 acid properties. The same author states that the bright 

 red colour of Polyporus cinnabarinus is due to the mixture 

 of a substance which forms beautiful cinnabar -red crystals, 

 denominated xantho-trametin, and also a resin. 2 In some 

 specimens of exotic species of Fomes we have sometimes seen 

 flakes of resin on the pileus which could be chipped off, but 

 could never be satisfied how they came there — whether from 

 the tree trunk which supported the Fungus, or as an exudation 

 from the Fungus itself. The varnished pileus of Fomes nigro- 

 laccatus becomes quite sticky soon after the application of 

 spirit to the surface. Fries mentions Polyporus resinosus as 

 exuding a resinous juice, and it is quite possible that some of 

 the woody Polypori which grow on coniferous trees will secrete 

 a considerable amount of resin, as they have a tendency to 

 become laccate when old. 



1 Joum. Roy. Micr. Soc, vol. vi. (1886), p. 486. 

 2 Bot. Zeit., vol. xlvii. (1889), p. 54, etc. 



