. Fungous diseases of plants : with chapters on physiology, culture methods and technique . Fungi in agriculture. 276 FUNGOUS DISEASES OF PLANTS produced. Some observers have recorded extreme sizes, 6-40 x l\-jp. More frequently, however (Von Schrenk), they are 12- 16 x 4-6/*. The conidia germinate readily, and upon germination almost invariably become septate. Under unfavorable conditions a germ tube may develop at its tip a brown resting cell termed a secondary conidium or appressorium. It is believed that the germ tube may obtain entrance to the fruit through the uninjured skin of the apple
. Fungous diseases of plants : with chapters on physiology, culture methods and technique . Fungi in agriculture. 276 FUNGOUS DISEASES OF PLANTS produced. Some observers have recorded extreme sizes, 6-40 x l\-jp. More frequently, however (Von Schrenk), they are 12- 16 x 4-6/*. The conidia germinate readily, and upon germination almost invariably become septate. Under unfavorable conditions a germ tube may develop at its tip a brown resting cell termed a secondary conidium or appressorium. It is believed that the germ tube may obtain entrance to the fruit through the uninjured skin of the apple, and certainly artificial infection may result without noticeable surface injury. Nevertheless, infection can be hastened by injuring the surface, and it is possible that some slight injury or abrasion may be essential to penetration, although the belief is cur- rent that entrance may be effected through the stomates of the Fig. 124. Glomerella rufomaculans: Conidial and Ascigerous Stages This imperfect form was for a long time the only known fruiting stage of the fungus. It was referred to the genus Glceosporium and was generally known as Glceosporium fructigenum Berk. The perithecial stage of this fungus, found by Clinton in 1902, may be readily developed in artificial culture, though Clinton has also reported having found it frequently upon the fruit. In cul- tures it may be developed within two weeks on various nutrient media, while in nature it develops apparently only the following spring upon fruit which has been upon the ground throughout the winter. In artificial culture the perfect stage develops promptly and vigorously upon apple agar corn meal. The mycelium first forms small black nodules which become stromatic cushions about one fourth inch in diameter. Within this stroma one or many peri- thecia might be developed. The various stages in the development. Please note that these images are extracted from scanned page images that may have been digitally enhan
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