FUNGI. 423 
lets of the roots of the wheat and corn, where the 
primitive spores and the large blunt spawn which 
they form could find no lodgment. In addition 
to the spores or conidia of the potato-blight, the 
fungus produces also zoospores or moving spores, 
furnished with the well-known moveable cilia, and 
capable of germinating and penetrating the tissues 
of the potato like the ordinary spores (Fig. 52). 
In the dewy autumnal mornings, when the potato- 
leaves are all moist, a few infected plants, by the 
aid of these swimming spores, will rapidly infect 
a whole field; while there is reason to believe 
that, in the form of oospores or sclerotia, the 
fungus hybernates during the nine months of its 
disappearance every year, and prepares itself for 
its annual attack in autumn. Furnished with 
such powers as these, it is a fortunate circum- 
stance that the fungi connected with vegetable 
epidemics require peculiar atmospheric and other 
conditions for their growth, and when these are 
absent they will not develop themselves or 
spread ; otherwise the whole world would be 
speedily overrun with them, and the fig-tree 
would not blossom, and there would be no fruit 
in the vines, the blossom of the olive would fail, 
and the fields would yield no meat. 
It is worthy of remark that the destructive 
effects of all these parasitic fungi may, in most 
