22 MICROSCOPIC PLANTS. {CHAP. 
but on the return of spring it germinates, and if po- 
tatoes are not near perishes. But if it is within reach 
of a potato tuber, it enters it; its mycelium pene- 
trates the haulm, and coming out into the air de- 
velops zoospores and conidia, and thus repeats the 
life-history given by Mr. Smith. From the experi- 
ments made with it, it is clear that a wet season is 
the most favourable to its growth, and the potato 
has less chance of recovering from its attack; but it 
is to be hoped that with the information recently 
obtained with reference to it, scientific men may be 
soon in a position to give such advice as will enable 
agriculturists to cope with this potent enemy. 
Fig. 22 represents another of these fungi which, 
like the Potato fungus, largely affect cultivators of 
the soil. This is the Ozdium Tuckeri, or Vine Blight, 
which attacks the Continental vineyards and even the 
hothouse vines in our own country; frequently it is 
Re 
the cause of great destruction. Recently it has been 
ascertained to be only one form of the fungus shown 
at fig. 23—LErysiphe, a species of which attacks the 
