266 



MYCOLOGY 



C. glceosporioides, clovers and alfalfa by C. trijolii and the snapdragon 

 by C. antirrhini. Usually the diseases on these plants induced by species 

 of Colletotrichum are known as anthracnose (Fig. 107). Coryneum Bei- 

 jerinckii is a destructive fungus causing the peach blight. Pestalozzia 

 Guepini var. vaccinii is a fungus often found upon the cranberry leaves 

 and fruits. The conidiospores are three-celled, the terminal cells with 

 filiform appendages. The shot-hole disease of plum and cherry is due to 

 Cylindrosporium padi. The formation of the acervuli is followed by the 

 falling out of the disease areas of the leaf resulting in the formation 



of the characteristic shot-hole. 

 The fruit spot of apples is caused 

 by C. pomii. 



III. HYPHOMYCETALES. 

 — The hyphae are septate, 

 branched in or on the substra- 

 tum. They are dark, or hyaline, 

 separate, or bound into coremia, 

 or layer-like cushions. The con- 

 idiospores may exist as oidio- 

 spores through the separation of 

 the hypha. The conidiophores 

 are simple, or branched. The 

 conidiospores of different shapes 

 and colors are borne in a variety 

 of ways on the conidiophores or 

 their branches. The genera may 

 be arranged in three series. 



A. MyceHum and spores light- 

 colored: Oospora, Monilia, 

 Oidium, Sporotrichum, Botrytis, Cephalothecium, Ramularia, Cercos- 

 porella, Piricularia. B . Mycelium dark-colored at least with age ; spores 

 generally dark: Fusicladium, Polythrincium, Scoletotrichum, Clado- 

 sporium, Helminthosporium, Macrosporium, Alternaria, Cercospora, 

 C. Conidiophores in the form of a tuberculate mass, or sporodochium : 

 Volutella, Fusarmm. As examples of common disease producing forms 

 of the above genera without enumerating all of the more important 

 species may be mentioned the potato scab fungus, Actinomyces chro- 

 mogenes, the early blight of potato fungus, Macrosporiums olani; the 



Fig., 108. — Sweet-potato stem rot 

 {Fusarium balatalis). Section through 

 sweet potato showing blackened ring just 

 below surface caused by the stem-rot fun- 

 gus. {After Harter, L. L., U. S. Farmers' 

 Bull. 714, March ii, 1916.) 



