PARASITISM 



305 



and so comprehends an enormous number of parasites. 

 Of these, familiar examples will be the "smut" upon 



FIG. 108. Dodder, a parasitic seed plant. A, Magnified section of stem 

 penetrated by roots of dodder; B, dodder upon a golden-rod stem; C, seedling 

 dodder plants growing in earth; h, stem of host; I, scale-like leaves; r, sucking 

 roots, or hanstoria; s, seedlings. (A and C after Strasburqer. From Bergen 

 and Davis' "Principles of Botany." Ginn & Co., polishers.) 



corn and rye, the potato "rot," the grape-vine "mil- 

 dew," the various "rusts," and some of the leaf curls. 



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