GEOGRAPHICAL DISTRIBUTION 329 



are not averse to heat, so long as there is plenty of moisture, 

 yet four-fifths of the species belong to a temperate climate. 



The next group in importance is that of the Polyporei, 

 with its 2200 species. This includes some genera which are 

 fleshy, and delight in a temperate climate ; but the majority 

 are of a leathery or woody substance, and can flourish in any 

 climate, but in many cases require a hot one. "We may com- 

 mence by excluding 257 species of Boletus and allied genera 

 which are fleshy, and partake of the character of the fleshy 

 Agarics, for their love of a temperate region. The old genus 

 Polyporus now constitutes four genera, of which Polyporus is 

 retained as the name of one genus, and includes the annual 

 species, which are at first soft, and prefer a temperate or warm 

 temperate climate. Of the 403 species, 210 are European or 

 North American, but chiefly in the southern parts, whilst 

 more than half the remainder enter the subtropical region. 

 The genus Fomes includes the hard woody species, which are 

 nominally tropical or subtropical, although a few will inhabit 

 temperate countries. One species, Fomes lucidus, is one of 

 the most cosmopolitan of Fungi, and is found all over the 

 world, except in the Arctic zone. Several other species have 

 a very wide range. The remaining genera, such as Polystidus, 

 Trametes, Daedalea, Hexagona, etc., extend through similar 

 countries to the equator, and together constitute the bulk of 

 the tropical Hymenomycetes. 



Very little more needs to be said respecting the Hymeno- 

 mycetes, since the remaining 2000 species follow the same 

 law of distribution, the fleshy to the temperate, the leathery 

 and woody to the subtropical and tropical regions. We 

 remarked of this, a quarter of a century ago, that when the 

 majority of the species of a genus are of a fleshy consistence, 

 it may generally be concluded that it belongs to a northern 

 region, even if it should have some representatives in lands 

 which enjoy more sunshine. Thus the species of Rydnum 

 are the principal ornaments of northern forests, where they 

 attain so luxuriant a growth and beauty that every other 

 country must yield the palm to Sweden in respect to them. 

 In Irpex and Radulum the texture is more coriaceous, and 

 hence we find the species more commonly inhabiting warmer 



