HYMENOMYCETES 137 



-with the tubes of the hymenium adhering so slightly to the 

 under side of the cap that they are easily removed. Otherwise 

 expressed, the trama of the pileus does not descend into the 

 tubes, the mouths of which constitute the pores. In all of 

 these a stem is invariably present, and sometimes a manifest 

 ring, but without a volva. They are usually of a robust habit, 

 sometimes attain a very large size, and are wholly terrestrial. 

 Like the fleshy Agaricini, they are most prolific in temperate 

 regions, being replaced in the tropics by woody Fomes or 

 leathery Polystidi, as fleshy Agarics are replaced by Lentinus 

 and Lenzites. The whole total of described species is some- 

 what under 300. 



Fistulina has a similar fleshy substance, but the stem may 

 be present or absent, and the tubes are not laterally adherent, 

 and nearly all the species grow upon decayed wood. 



The genus Polyporus, as originally characterised by Fries, 

 was a large one and spread all over the world, but in recent 

 times it has shared the fate of other large genera, and been 

 subdivided into the genera Pohjporus, Fomes, Polystidus, and 

 Porta, as suggested by Fries in one of his latest works. These 

 appear to be well defined, and no difficulty will be found to 

 occur practically in their discrimination. The original name is 

 retained for the section Anodcrmei of the old, undivided genus. 



The pileus is at first soft and fleshy but tough, becoming 

 indurated, rarely fragile, without furrows or zones on the 

 pileus, and with only a single stratum of tubes, so that practi- 

 cally they are not perennial. Some of the species have a 

 central stem, and then resemblf" Boletus, only that the trama 

 of the pileus is continuous with » ^e tubes, which are not easily 

 separable from the flesh of the cap. Other species have a 

 lateral stem, or even a common stem, much divided above, and 

 bearing several pilei (Fig. 52). Finally, other species have no 

 stem at all, and the pileus is broadly attached to the matrix, so 

 as to be semi-orbicular or kidney-shaped. Earely the pileus is 

 reduced to a thin stratum, adherent by its whole surface, as in 

 Poria, but with a slightly reflexed margin. In Fomes the 

 substance is woody from the first, becoming very hard, and 

 covered with a rigid crust ; not truly zoned, but becoming con- 

 centrically sulcate. The substance is floccose and interwoven, 



