34 INTRODUCTION TO THE STUDY OF FUNGI 



No one has yet paid much attention to the coloration of 

 the pileus in Agaricini, which is subject to much variation, 

 due in part to external circumstances, as was pointed out by 

 M. de Seynes. Albinism is one of the variations which he 

 observed in well-recognised species. It occurs in Hygrophorus 

 calyptraeformis, Amanitopsis vaginata, Russula fragilis, and 

 some others. " By the side of this fact there is another quite 

 opposite, the greater intensity of coloration, according to the 

 temperature.'' For instance, he found during the winter 

 Tricholoma nuda, according as the temperature falls, of a dark 

 violet, almost black, or a deep brown. When spring arrives 

 it is found almost white, shaded with lilac or fawn colour. 

 Tricholoma terreus and Collybia dryophilus will present the 

 same phenomena. He' found also, in a cold December, Volvaria 

 media of which the pileus was almost black ; ordinarily it is 

 nearly white. Upon microscopical examination he found that 

 there was no new production of cellular elements, but simply 

 a greater agglomeration of pigmentary granules. He also 

 indicates that he has often been struck with the deep colora- 

 tion of Armillaria mellea and Hypholoma sublateritius, which 

 were seen by hundreds during a low temperature (41° to 42° 

 Fahr.), the aspect of which differed very much from the same 

 species found in the woods during the fine days of autumn. 1 

 The same writer adds that, from numerous observations, he is 

 certain that, although the cold has an influence upon the 

 intensity of coloration amongst Agarics, it does not follow that 

 in the middle of winter specimens may not be found of the 

 normal colour, either by being shaded, or in proximity to heat. 

 The effects of external circumstances on the variation of the 

 fleshy Fungi deserves more serious attention. 



In some few instances the fleshy stratum is almost obsolete 

 over the entire cap, as in Hiatula, some species of Coprinus, 

 Bolbitius, etc., and in some exotic species of Marasmius. In 

 such cases the cap is so thin — like a membrane — that when 

 moist the gills may be seen through the substance. In 

 Boletus the cuticle is sometimes distinctly velvety, and the 

 flesh is comparatively thicker than in Agarics. In Polyporus, 

 Fomes, Polystictus, Rydwwm, etc., the entire substance is more 

 1 Grevillea, vol. ii. p. 12. 



