TREMELLA MYCETOPHILA 465 



grow in contact with the hyphae of the host without any chemo- 

 tropic repulsion. For further advances in our knowledge of the 

 parasitism of agarics which live on other agarics we must look, in 

 the main, to the biochemist. 



CoUybia dryophila and its Pseudoparasite Tremella myceto- 

 phila. — CoUybia dryophila is a well-known agaric commonly found 

 in woods both in Europe and North America. In its general appear- 

 ance it is reminiscent of CoUybia butyracea, C. velutipes, and some 

 other species of CoUybia ; but it has the property of reviving 

 in wet weather after being dried '^ and has therefore been placed by 

 Rea ^ and some other systematists in the genus Marasmius. Its 

 spores are white and, on the average, measure 5-4 x 3-2 yu,.^ A 

 single spore begins its development on the end of a sterigma, grows 

 to full size, matures, and is discharged all within a space of time 

 which somewhat exceeds one hour.'* When a dried up fruit-body 

 is wetted by a shower of rain, it very quickly absorbs water through 

 the upper surface of its pileus, its basidia then resume their develop- 

 ment and, within an hour or two, the pileus begins to liberate spores 

 once more. 



The gills of CoUybia dryojjhila are crowded together. When in 

 an expanded lamellated fruit-body the gills are distinctly crowded, 

 the spores are usually of small size ; and, generall}', in the Agari- 

 cineae, there seems to be a correlation between the crowding of 

 the gills and the size of the spores of such a nature that, on the 

 whole, the more crowded the giUs, the smaUer the spores.^ Thus, to 

 take extreme examples, in CoUybia dryojjhila, C. maculafa, Clitocybe 

 nebularis, and Panus stypticus, all of which have crowded gills, the 

 size of the spores is 5-6 x 3-4 /x, 5-G fx, 7-8 x 3-4 /x, and 4-5 x 

 2-25 fi, respectively; while in CoUybia radicata, C. platyphylla, 

 Gomphidius viscidus, and Amanitopsis vaginata, all of which have 

 relatively distant gills, the size of the spores is 14-15 x 8-9 fj-, 



1 These Researches, vol. i, 1909, pp. 107, 108, 111. 



- Carleton Rea, British Basidiomvcetae, Cambridge, 1922, p. 524. 



^ These Researches, vol. i, p. 162. 



* These Researches, vol. ii, 1922, p. 49. 



^ Small spores are correlated with small basidia, and large spores with large 

 basidia {cf. vol. ii, p. 412), so that one might also say : the more crowded the gills, the 

 smaller the basidia. » 



VOL. III. 2 H 



