94 



FU]^GI AND FUis-GICIDES 



threads which run over the surface of the leaf, and 

 obtain nourishment by sending down into the cells short 

 branches^ often called suckers. During the summer 

 these threads also send ujDward in the air certain other 

 branches, which gradually divide into a number of 

 parts, as shown in a, Fig. 46, and thus j)roduce the 

 summer spores, or couidia. These summer spores are 

 very light, and are blown about by the wind ; when one 

 falls upon a damp gooseberry leaf it germinates by send- 

 ing out a slender tube, from which the mildew starts 

 anew. As the summer spores are unable to survive the 

 winter, the fungus produces, especially late in the sea- 



son, another kind of spores, the so-called winter spores. 

 These are much more complicated in structure than the 

 others. As seen under the microscope, they consist 

 externally of a small round case, from which project 

 about a dozen short delicate appendages, like those rep- 

 resented in 5, Fig. 46. This is the outer spore case 

 (called by botanists the perithecium). If it be crushed 

 it will break open on one side, and there will be pushed 

 out a flattened oval body — the inner spore case, or ascus 

 —within which may be seen eight small bodies, which 

 are the spores (5). By means of these the fungus sur- 

 yiyes the winter. 



a 



FIG. 46. SPORES OF GOOSEBERRY mLDEW. MAGNIFIED. 



