. Fungous diseases of plants, with chapters on physiology, culture methods and technique . d by the development ofa stromatic mass of myceliumbeneath the epidermis. Fromthis stromatic mycelium theredevelops a cone-shaped massof erect hyphae which eventu-ally rupture the cell there are producedfrom the numerous, erectconidiophores an abundanceof conidia. When the epider-mis is ruptured, these conidia emerge as a waxy, tendril-like strand,which may be at first pink in color, becoming gray with age. Thespores are then imbedded in a gelatinous matrix readily soluble inwater. Little
. Fungous diseases of plants, with chapters on physiology, culture methods and technique . d by the development ofa stromatic mass of myceliumbeneath the epidermis. Fromthis stromatic mycelium theredevelops a cone-shaped massof erect hyphae which eventu-ally rupture the cell there are producedfrom the numerous, erectconidiophores an abundanceof conidia. When the epider-mis is ruptured, these conidia emerge as a waxy, tendril-like strand,which may be at first pink in color, becoming gray with age. Thespores are then imbedded in a gelatinous matrix readily soluble inwater. Little may therefore be seen of the strand-like productionof the spores during moist weather, or even during a period ofheavy dews. Fig. 124 shows the relation of the conidiophores tothe mycelial stroma. Examined microscopically the conidia arealmost hyaline, though having a slight greenish cast. They vaiyin shape from ovate to oblong, or in some cases even slightlydumb-bell-shape. In general, however, they are ovoidal and varygreatly in size, according to the conditions under which they are. Fig. 123. Canker of the Bitter RotFungus. (Photographby Parley Spaulding) 276 FUNGOUS DISEASES OF PLANTS produced. Some observers have recorded extreme sizes, 6-40 x3I-7/1. More frequently, however (Von Schrenk), they are 12-16 X 4-6 fi. The conidia germinate readily, and upon germinationalmost invariably become septate. Under unfavorable conditionsa germ tube may develop at its tip a brown resting cell termed asecondary conidium or appressorium. It is believed that the germtube may obtain entrance to the fruit through the uninjured skinof the apple, and certainly artificial infection may result withoutnoticeable surface injury. Nevertheless, infection can be hastenedby injuring the surface, and it is possible that some slight injur}- orabrasion may be essential to penetration, although the belief is cur-rent that entrance may be effected through the stomates of the fruit.
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