270 FUNGI. 



cuttings, of more or less extensive swamps, or from the cul- 

 tivation of the soil — all of them circumstances which cause the 

 destruction of the primitive fungaceous vegetation and the pro- 

 duction of a new one. If we compare the fungal flora of America 

 with that of European countries, we observe that the former 

 equals, in its richness and the variety of its forms, that of the 

 phanerogamous flora; it is probable, however, that, in the 

 lapse of more or fewer years, this richness will decrease, in 

 consequence of the extension of cultivation—as is illustrated, 

 indeed, in what has already taken place in the more thickly 

 peopled districts, as, for example, in the vicinity of New 

 York." 



Although heat and humidity influence all kinds of vegetation, 

 yet heat seems to exert a less, and humidity a greater, influence 

 on fungi than on other plants. It is chiefly during the cool 

 moist autumnal weather that the fleshy fungi flourish most 

 vigorously in our own country, and we observe their number to 

 increase with the humidity of the season. Rain falls copiously 

 in the United States, and this is one of the most fruitful coun- 

 tries known for the fleshy fungi. Hence it is a reasonablo 

 deduction that moisture is a condition favourable to the develop- 

 ment of these plants. The Myxogastres, according to Dr. Henry 

 Carter, are exceedingly abundant — in individuals, at least, if not 

 in species — in Bombay, and this would lead to the conclusion 

 that the members of this gronp are influenced as much by heat 

 as humidity in their development, borne out by the more plen- 

 tiful appearance of the species in this country in the warmer 

 weather of summer. 



In the essay to which we have alluded, Fries only attempts 

 the recognition of two zones in his estimate of the distribution 

 of fungi, and these are the temperate and tropical. The frigid 

 zone produces no peculiar types, and is poor in the number of 

 species, whilst no essential distinction can be drawn between the 

 tropical and- sub-tropical with our present limited information. 

 Even these two zones must not be accepted too rigidly, since 

 tropical forms will in some instances, and under favourable con- 

 ditions, extend far npwards into the temperate zone. 



