Fungous diseases of plants . ht be considered varietal orracial, and in some instanceswe have unquestionably to dowith physiological forms. It iscertain, however, that Rliizoc-tonia Medicaginis De C. ofEurope is a fungus very differ-ent from the common potatofungus of Europe and Americaand also from the commonspecies producing damping-offof seedlings, rot of beets, etc.,in this country. Moreover, aform which has been described(Duggar and Stewart) on rhu-barb is likewise a very differentorganism. It would not, how-ever, be surprising to find thata very large number of theother forms which have
Fungous diseases of plants . ht be considered varietal orracial, and in some instanceswe have unquestionably to dowith physiological forms. It iscertain, however, that Rliizoc-tonia Medicaginis De C. ofEurope is a fungus very differ-ent from the common potatofungus of Europe and Americaand also from the commonspecies producing damping-offof seedlings, rot of beets, etc.,in this country. Moreover, aform which has been described(Duggar and Stewart) on rhu-barb is likewise a very differentorganism. It would not, how-ever, be surprising to find thata very large number of theother forms which have beendiscussed by various authors may be ascribed to one and the samespecies, the perfect stage of which would now appear to be Corti-cium vagnvi B. &C. var. Solani Burt. Effects upon the hosts. The fungus is perhaps most disastrousas a damping-off disease. The progress of the disease upon seed-lings resembles very closely that of Pythium, and it is affected bysimilar conditions. The plants that have thus far seemed to be. Fig. 2i8. Rhizuctijma u.\ Radish(Photograph by H. H. Whetzel) AUTOBASIDIOMYCETES 447 most susceptible are such as lettuce (Fig. 217), sugar beet, celery,cotton, and the seedlings of various delicate, ornamental plants. Upon the potato the fungus has been known for more thanhalf a century in Europe, but largely through the presence of asclerotial stage upon the tubers. This typical sclerotial stage
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