Fungous diseases of plants . Fig. 123. Canker uf the Bitter RotFungus. (Photographby Perley Spaulding) 276 FUNGOUS DISEASES OF PLANTS produced. Some observers have recorded extreme sizes, 6-40 x3i-7yu,. More frequently, however (Von Schrenk), they are 12-16 X 4-6/Lt. 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
Fungous diseases of plants . Fig. 123. Canker uf the Bitter RotFungus. (Photographby Perley Spaulding) 276 FUNGOUS DISEASES OF PLANTS produced. Some observers have recorded extreme sizes, 6-40 x3i-7yu,. More frequently, however (Von Schrenk), they are 12-16 X 4-6/Lt. 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 injury orabrasion may be essential to penetration, although the belief is cur-rent that entrance may be effected through the stomates of the Fig. 124. Glomhrella rufomaculans:(Zos\d\\\. and Ascigerous Stages This imperfect form was for a long time the only known fruitingstage of the fungus. It was referred to the genus Gloeosporiumand was generally known as Ghvosporiiim fructigcjimn Berk. The perithecial stage of this fungus, found by Clinton in 1902,may be readily developed in artificial culture, though Clinton hasalso reported having found it frequently upon the fruit. In cul-tures it may be developed within two weeks on various nutrientmedia, while in nature it develops apparently only the followingspring upon fruit which has been upon the ground throughout thewinter. In artificial culture the perfect stage develops promptlyand vigorously upon apple agar corn meal. The mycelium firstforms small black nodules which become stromatic cushions aboutone fourth inch in diameter. Within this stroma one or many peri-thecia might be developed. The various stages in the development ASCOMVCETES 277 of the perithecium have not been
Size: 2430px × 1028px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, bookpublisherbostonnewyorketcgi
