Minnesota Plant Diseases. 



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at least in higher forms, is highly organized. In lowly forms of 

 fungi, where the plant body is but a single, small, more or less 

 rounded cell of microscopic size, absorption takes place over 

 the entire surface of the little plant and there is no specialized 

 region for the performance of this function. In all of the higher 

 forms absorption takes place through a system of much- 

 branched, fine threads of microscopic size. 



In a mushroom, for instance, these threads penetrate the 

 soil for a considerable distance, often for feet and even yards. 



m 



Fig. 2. — Various special absorptive or sucker threads of parasitic fungi, m. The mycelial 

 threads. The sucker threads (H) are seen in the host plant cells. I. A downy 

 mildew. II. Rust fungus. III. Protomyces (a fungus with a doubtful systematic 

 position). Highly magnified. After Zopf. 



The absorptive area is built upon a similar physiological prin- 

 ciple to that of the root system of. flowering plants, for in these 

 absorption takes place at the surface of very fine hairs, which 

 are borne on the surface of the younger roots. True root hairs 

 and fungus absorption threads embody the same advantage in 

 the presentation of a large absorbing area. In the fungus the 

 threads branch profusely and are of great length, and thus a 



