PAEASITIC FUNGI AND MOULDS. 27 



produced in the yellow balls correspond with those 

 which issue from the asci developed on the sclerotis ; 

 these are endogenous spores. 



Many of the parasitic fungi belonging to the genera 

 Erysiphe, Sphceria, Sordaria, Penicillium, etc., pre- 

 sent a similar mode of vegetation, and affect a large 

 number of plants. Such is the Oidium of the vine 

 (Erysiphe Tuckeri} to which we shall presently revert. 



IV. OOMYCETES, MUCORINE.E, OR MOULDS, PROPERLY 

 SO CALLED ; PERONOSPORE.E ; THE POTATO-FUNGUS. 



In all the parasitic fungi of which we have hitherto 

 spoken there is no sexual reproduction analogous to 

 that of the higher plants ; there are no male and female 

 organs comparable to the stamens and pistil. This 

 sexual reproduction exists in the oomycetes, although 

 only in a very elementary form. In 

 addition to the ordinary spores which 

 we have noticed in other fungi, there 

 are others termed oospores, which are 

 formed by the fusion of the originally 

 distinct contents of two different 

 cells. In the family of the mucorinege, 

 which includes most of the fungi 

 commonly called moulds (Fig. 14), 

 the two cells of which the contents 

 are fused together are similar. In the peronosporeae, 

 however, which includes the potato-fungus, one of the 



