274 M. E. P. Fries on the Geographical 
One of the most remarkable circumstances in the history of 
the lower Fungi is that of their sudden appearance in immense 
numbers, and their rapid extension, whence, particularly of late 
years, some disastrous and destructive epidemics, both among 
animals and plants, have resulted,—as, for example, the ravages 
produced by the Ozdium Tuckeri, the cause or the manifestation 
of the vine-disease; or the plague-like epidemic of the silk- 
worm, from the attacks of the Stachylidium Bassianum ; or the 
destruction of the common Flies, usually resulting from the pa- 
rasitic growth of the Sporendonema Musce. The potato-disease 
is also accompanied by the growth of several Mucedines; but 
their presence nevertheless is evidently nothing more than the 
consequence, and not the efficient cause, of the morbid affection. 
As another example, it is well to mention the Lanosa nivalis, 
which grows in spring in the melting snow, and is suspected to 
be the cause, in many instances, of the death of the germs of the 
sprouting rye. 
The semi-Fungi (Discomycetes and Pyrenomycetes) exhibit 
genera characterized sometimes by a hard and carbonaceous, 
and at other times by a soft and somewhat waxy texture. The 
latter consistence predominates among the Discomycetes, and the 
woody texture among the Pyrenomycetes. The last-named, 
again, are slow in growth; whereas the Discomycetes increase 
rapidly, and, moreover, resemble in their mode of development, 
in many respects, the Hymenomycetes. 
The Pyrenomycetes, particularly those that attain the greatest 
development, have a more extended geographical range than any 
other of the Fungi. They are to be met with everywhere, except 
in water [one species, however, the Spheria Posidonia, always 
vegetates under water], and especially where vegetation of any 
sort is in process of decay. In fact, they possess a high import- 
ance in the general economy of nature, because they accelerate 
the decomposition of dead and dying organisms. The richer the 
vegetation of a country is, the more numerous and varied are the 
forms of Pyrenomycetes to be found there. 
The more highly developed Pyrenomycetes evidently have 
their geographical centre in the torrid and temperate zones ; 
their dimensions and astonishing variety of form increase to the 
south of the equator, as is instanced in the genera Xylaria, Do- 
thidea, Diatrype, &c.; in the same way Spheria and Hypoxy- 
lon, between the tropics, vegetate under an infinite variety of 
forms, for the analogues of which it is vain to seek in the forests 
of Europe. The superior Discomycetes, on the contrary, such as 
the Helvellacese (Morchella, Gyromitra, Helvella, Geoglossum, 
&c.) and the Bulgariacee (Leotia, Bulgaria), grow by prefer- 
ence in the colder portions of the temperate zone. This circum- 
