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 Oidium Tuckeri, or Vine Blight, 

 which attacks the Continental vineyards and even the 

 hothouse vines in our own country; frequently it is 



FIG. 23. 



FIG. 22. 



the cause of great destruction. Recently it has been 

 ascertained to be only one form of the fungus shown 

 at fig. 23 Erysiphe, a species of which attacks the 



