184 INTRODUCTION TO THE STUDY OF FUNGI 



such problems to solve in connection with discoid Fungi, but 

 the facts are few and the inferences are not self-evident. In 

 certain isolated cases they may be, but they concern mostly 

 only the species in question, and are not of general application. 

 Take, for instance, the case of Geapyxis ammophila. Here is a 

 Peziza of considerable size, of the colour of sea-sand, the 

 exterior usually covered with particles of sand, and the base 

 attenuated into a tapering root three times in length that of 

 the cup. When it is known that this species is found only on 

 loose sandy dunes, it is at once concluded that the long rooting 

 base serves a useful purpose in attaching the Fungus well into 

 the loose sand and thus preventing its drifting away to 

 destruction, whilst the inconspicuous colour masks its presence 

 and prevents its being designedly uprooted. But it is not 

 always evident, as in this case, what is the purpose of the 

 peculiarity. The semi-subterranean species of Sepultaria are 

 mostly of some shade of brown, and the exterior is covered 

 with a dense matting of interwoven hairs. They affect a 

 globose form, with the disc but slightly exposed, except when 

 saturated with moisture. Blown away from their attachment, 

 their form assists them in being transported from place to 

 place, until a wet locality is reached, when the cup more or 

 less expands, and they drift no more until again dried and 

 closed, when the globose form is resumed. The colour, ap- 

 proximating that of the soil, may be deemed a protection, and 

 the dense woolly coat a means of retaining moisture, as well as 

 preventing rapid evaporation and consequent desiccation. But 

 that which may be true. enough of one species, or of one series 

 of species, is not necessarily a theory of universal application. 

 It is true that nearly all the species of Ascdbolus which grow 

 upon dung are so inconspicuous that they can only be 

 distinguished from the matrix by close observation. It might 

 be inferred that this accommodation of colour was intended 

 for the preservation of the individual and the perpetuation of 

 the species. This would not apply, however, to Humaria 

 granulata, which is very common in large patches, of a bright 

 orange colour, on the same matrix, very conspicuous at a 

 considerable distance. In this instance colour can be no 

 protection, but what is the purpose of the bright colour ? 



