. Black rot, leaf spot and canker of pomaceous fruits. Black rot; Leaf spots; Canker (Plant disease); Apples. Black Rot, Leaf Spot, and Canker of Pomaceous Fruits 107 pycnospore germination (Fig. 29). The pycnospores usually ger- minate readily in tap or rain water. The time required for the process varies considerably, depending, no doubt, on the age of the spores. If they overwinter, the question of their longevity arises. As a rule sexual spores are regarded as short-lived, but it is not so in the case of this fungus. Duggar (1909:353) says: "The spores seem to retain their vitality fo
. Black rot, leaf spot and canker of pomaceous fruits. Black rot; Leaf spots; Canker (Plant disease); Apples. Black Rot, Leaf Spot, and Canker of Pomaceous Fruits 107 pycnospore germination (Fig. 29). The pycnospores usually ger- minate readily in tap or rain water. The time required for the process varies considerably, depending, no doubt, on the age of the spores. If they overwinter, the question of their longevity arises. As a rule sexual spores are regarded as short-lived, but it is not so in the case of this fungus. Duggar (1909:353) says: "The spores seem to retain their vitality for a considerable period of time, having been germinated after being stored for a year in the ; The writer has found that spores two years old or older may germinate in tap water after twenty-four hours. Younger spores ordinarily germinate within five or six hours, but they may pro- duce a tube after three hours. Spores which are dark brown in color, often septate, and having an older appearance, re- quire more than twelve hours for germination. Usually one or two tubes emerge from a spore at or near the end; germinations also occur at the side. The de- veloping hypha? in cul- ture occasionally form microconidia, or second- ary conidia, near the growing point of a hypha; these have been men- tioned by* D e1 a c roi x (1903 a: 139), who states that they do not develop further. The writer has germinated them in tap water. In some cases peculiar types of germination occur, short, stunted tubes being developed. In other cases the process is entirely inhibited, and in certain of these cases the laying down of a cross-wall takes place instead. In one obser- vation notes were made as follows: Spores one-celled when collected (May 13, 1913). Placed to germinate in tap water and after twenty-four hours the two-celled spores had not germinated; the one-celled spores had developed tubes about 30ji long. After forty-two hours some of the two- celled spores developed tubes ab
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectblackro, bookyear1916
