270 FUNGI. 
cuttings, of more or Icss extensive swamps, or from the cul- 
tivation of the soil—all of them circumstances which cause the 
destruction of the primitive fangaceous 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 Mfyxogastres, 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 group 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 upwards into the temperate zone. 
