Fungous diseases of plants . ed the geneticconnection between the Macrosporium of onion and Plcospora hcr-bariivi (Pers.) Rab., incidentally indicating, also, that the Macrospo-rium agrees with the saprophytic form described by Berkeley. XV. MACROSPORIUM: OTHER SPECIES Occurring upon other solanaceous hosts are such species asMacrosporiuvi toviato Cke. and Macrosporium Datura species have been reported upon onions besides Macro-sporhini Sarci)iula Berk, above discussed. Other species ofMacrosporium besides the latter have also been connected withspecies of Pleospora. Macrosporium
Fungous diseases of plants . ed the geneticconnection between the Macrosporium of onion and Plcospora hcr-bariivi (Pers.) Rab., incidentally indicating, also, that the Macrospo-rium agrees with the saprophytic form described by Berkeley. XV. MACROSPORIUM: OTHER SPECIES Occurring upon other solanaceous hosts are such species asMacrosporiuvi toviato Cke. and Macrosporium Datura species have been reported upon onions besides Macro-sporhini Sarci)iula Berk, above discussed. Other species ofMacrosporium besides the latter have also been connected withspecies of Pleospora. Macrosporium nigricantiiim Atkinson, Macrosporium Tabaci-num Ell. & Ev., and Macrosporium Iridis C. & E. are commonlyreported as leaf spot or blight fungi of their respective hosts, cot-ton (Gossypium), Iris, and tobacco {Nicotiana Tabacum). FUNGI IMPERFECTI 305 XVI. BLIOHT OF GINSENG 1 AHcniaria Panax Whetzel Occurrence and symptoms. The so-called blight is the mostcommon and destructive disease of cultivated ginseng. It occurs. Fig. 138. Blight of Ginseng: a Frequent Form of the Disease(Photograph by H. H. Whetzel) apparently throughout the eastern United States wherever ginsengis grown, but has not been with certainty reported west of theMississippi. The disease is caused by Alternaria Panax Whetzel, ^ This account of the blight of ginseng was kindly prepared by Professor Whetzel, Cornell University. 3o6 FUNGOUS DISEASES OF PLANTS which, in its general characters, as regards spores (size, shape, etc.),is very much Hke the Altcrnaria Solaiii producing the early blightof potatoes. The fungus is a genuine parasite, attacking plantsboth young and old, and apparently under all conditions, althoughthe disease becomes epidemic only in hot rainy weather. The parasite attacks all of the parts of the plant above ground,but never affects the roots. During epidemic periods the diseaseworks with great rapidity, so that the tops of plants in an entiregarden may be entirely destroyed within a few
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