. Black rot, leaf spot and canker of pomaceous fruits. Black rot; Leaf spots; Canker (Plant disease); Apples. Such hyphas are regarded as being intercellular, merely giving the appear- ance of an intracellular habit because of the thickness of the section; in thin, microtomed sections the threads are found be- tween the cells. In certain cases the hyphre appear to be within the cells, but one may mistake a large intercel- lular space for a cell lumen. Dandeno (1906) states that the mycelium is intercellular, but that small threads enter the cells and even pass through them (Fig. 31). Leaves.—
. Black rot, leaf spot and canker of pomaceous fruits. Black rot; Leaf spots; Canker (Plant disease); Apples. Such hyphas are regarded as being intercellular, merely giving the appear- ance of an intracellular habit because of the thickness of the section; in thin, microtomed sections the threads are found be- tween the cells. In certain cases the hyphre appear to be within the cells, but one may mistake a large intercel- lular space for a cell lumen. Dandeno (1906) states that the mycelium is intercellular, but that small threads enter the cells and even pass through them (Fig. 31). Leaves.— The lesion pro- duced on the leaf is largely necrotic. The cells are brown, collapsed, and ob- viously dead. The average thickness of 'the normal apple leaf is about 142 (i, whereas that of the diseased area is about 61 n (Fig. 32). The epidermal cells of the affected tissue are flattened and bear little resemblance to normal epidermis. The palisade cells maintain their relative position but are considerably shortened. The cells of the spongy parenchyma are shriveled and irregular in form (Fig. 32). In some cases the lesions are limited by a vein, and, although a small vein may mark the extent of the diseased area, the larger veins more frequently act in this capacity. In cases in which the edge of the spot does not fall at a vein, a plate of cells surrounds the lesion and limits, for a time at least, the extent of the fungus. The structure of the leaf at the margin of a spot is very different from either the healthy or the dead parts. The process of differentiation apparently takes place in considerable advance of the fungus. In some stained sections HISTOLOGICAL CH \NGES IN THE FRUIT OF APPLE Showing appearance of healthy tissue at left and diseased tissue at right, and the mycelial relationship to the host cells. Fig. HISTOLOGICAL CHANGES LEAF TISSUE IN DISEASED Showing healthy and diseased tissue. The beginning of the subenzed layer, represented by heavy-walled cells in a
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectblackro, bookyear1916
