PARASITIC FUNGI AND MOULDS. 17 



the complete development of the fungus is only effected 

 by its transference from one plant to another. This 

 phenomenon may be frequently observed in animal 

 and vegetable parasites, and it seems to be designed 

 in order to secure the preservation of the parasitic 

 species, by permitting it to grow on two plants in 

 succession, of which the development occurs at different 

 periods of the year ; such is the case with the barberry, 

 which is developed in early spring, while wheat is 

 developed in summer. For a long while it was 

 believed that (Eeidium berberidis, Uredo linearfe, 

 and Puccinia graminis were so many distinct 

 species; but it is now known, as we have stated, 

 that they are only three successive phases of the 

 development of a single species.* 



Other Uredinece, constituting the modern varieties 

 of Ustilago and Tilletia, are more apt to affect the 

 ears of wheat and other grasses. This disease is termed 

 by agriculturists smut or caries (Uredo carlo or 

 Ustilago segetum, and Tilletia caries). The diseased 

 grain merely appears to be of a somewhat darker 

 colour, but on pressing it between the fingers, there 

 issues from it a blackish, oily pulp, which smells 

 like rotten fish. Bread made from the flour of such 

 corn has an acrid and bitter taste, and although it 

 does not appear to be directly injurious to health, 



* So, again, (Eeidium rhamni (Nerprun or Boimlaine) produce 

 Uredo rubiyo-vera and Piicciuia coronata of wheat and oats. (See 

 Fig. 7.) 



