. Black rot, leaf spot and canker of pomaceous fruits. Black rot; Leaf spots; Canker (Plant disease); Apples. 114 Bulletin 379 there is a streak developed in the outer layers of wood (Fig. 34), just as in the twig blight on chestnut oak, Quercus prinus, as reported by Ingram (1912) and noted subsequently by Rankin (1914). The streak is due to the discoloration of the ceils, not to the presence of the mycelium (Figs. 35 and 36). One has only to examine longisections through the streak to be convinced that the hyphal threads do not grow in strands and are not otherwise arranged so as to give suc
. Black rot, leaf spot and canker of pomaceous fruits. Black rot; Leaf spots; Canker (Plant disease); Apples. 114 Bulletin 379 there is a streak developed in the outer layers of wood (Fig. 34), just as in the twig blight on chestnut oak, Quercus prinus, as reported by Ingram (1912) and noted subsequently by Rankin (1914). The streak is due to the discoloration of the ceils, not to the presence of the mycelium (Figs. 35 and 36). One has only to examine longisections through the streak to be convinced that the hyphal threads do not grow in strands and are not otherwise arranged so as to give such an appearance to the tissue. In the case of the more superficial cankers the ingress of the fungus is cut off from the healthy tissue by the development of a cork layer (Fig. 37). Such lesions reveal in section the presence of a layer approximating the normal periderm, with which it is continuous and which reacts the same with safranine and with a chloro- phyll solution. These cells in their final state are suberized. The layer originates by the di- vision of cells of the cortical paren- chyma. The sclerenchyma fibers are not changed. If the layer comes in contact with a group of sclerenchyma fibers it is inter rupted. The more recently affectec cells—that is, those nearest the margin of the lesion — show a red- dish tinge with safranine, indi- cating slight suberization through- out the region. Later, evidence of the cork layer is found just beyond the infected zone. Walls are laid down to form rectangular cells characteristic of the final cork 'layer and of the normal periderm. At this time they do not take the safranine, indicating that suberization has not begun. Such sections stained with chlorophyll solution also show no suberin reaction. A later examination of the marginal layer between healthy and diseased tissue stained with safranine will reveal three distinct and characteristic zones, as follows (enumerating entad): a red layer of three or four suberized cork c
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectblackro, bookyear1916
