SECT. in. PROFUSION OF FUNGI. 297 



world; they grow on fat, on greasy walls, and on de- 

 caying fruit and vegetables. 



The extreme minuteness of the reproductive bodies 

 of the microscopic fungi, many of which are not more 

 than the 20,000th part of an inch in diameter, and their 

 extraordinary and varied forms even in the same plant, 

 have made these fungi one of the most difficult studies 

 in the whole science of botany. There is still some 

 obscurity with regard to those minute motile bodies 

 supposed to be male particles, and their analogues, 

 which have not been seen, or have rarely been seen to 

 germinate. These bodies have been observed in com- 

 paratively few genera, and nothing more than mere 

 molecular motion has been observed in them. 



One of the most unaccountable circumstances in the 

 history of the lower fungi is their sudden appearance 

 in immense numbers, and the rapid extension of dis- 

 astrous and destructive epidemics caused by them 

 among plants and animals, as the potato murrain 

 and the vine disease, which, though widely spread 

 through Europe and Madeira, leaves the North American 

 vines unscathed, whether grown at home or abroad. 

 The black mildews at one time raged so much in the 

 Azores and Ceylon as to threaten the complete anni- 

 hilation of the orange and coffee plantations. Their 

 ravages have been scarcely less among the olive trees 

 in some parts of Europe ; and the Lanosa nivalis, which 

 grows in the melting snow in spring, is supposed to be 

 the cause in many instances of the death of the germs 

 of the sprouting rye. The destructive course of most 

 of these has abated, but the silkworm disease still 

 continues. The fungi require warmth and a moderate 

 degree of moisture for their development, but the un- 

 wonted multitudes in which the parasites occasionally 

 appear, possibly indicate some meteoric influences of 

 which we are ignorant. 



