. A contribution to the morphology and biology of insect galls [microform]. Galles (Botany); Galls (Botany). «9"1 MOKPHOLOGY AND BlOLOGY OF INSECT GallS 3«5 As in the preceding galls descnbed, the principal part of the gall tissues ill this species is originated from the vascular bundles and paren- chyma strands (Fig. 17). The latter are very wide and the abnormal cell division is more marked in them than in the bundles. The wood elements produced remain undifferentiated and pith-like. The cuticle of the gall epidermis is much stronger than that found in the normal stem. The epidermis its
. A contribution to the morphology and biology of insect galls [microform]. Galles (Botany); Galls (Botany). «9"1 MOKPHOLOGY AND BlOLOGY OF INSECT GallS 3«5 As in the preceding galls descnbed, the principal part of the gall tissues ill this species is originated from the vascular bundles and paren- chyma strands (Fig. 17). The latter are very wide and the abnormal cell division is more marked in them than in the bundles. The wood elements produced remain undifferentiated and pith-like. The cuticle of the gall epidermis is much stronger than that found in the normal stem. The epidermis itself has responded to the stimulation by the production of an extra layer of cells. The cortex of the gall contains approximately one-third more cell layers than the normal cortex as seen in Fig. 18. The normal stem of Ceanothus americanus L. contains glands in the cortex. These are fairly regularly spaced around the stem but are larger and more numerous at the nodes. Glands occur also in the pith of the stem, the petioles of the leaves and the reproductive axes. But in parts of stems, contiguous with galls, though glands occur in the pith there are none in the cortex, except at the nodes. Glandular cells, however, are plentiful in the cortex of such stems. A cross section of a gall shows larger and more numerous glands than a corresponding section of the normal stem. The probable ex- planation of this is that owing to the shortening of the stem axis, nodes are cut more frequently. In the gall cortex there are also narrow, eko. ated, glandular cavities, that do not seemingly correspond to anything seen in the normal stem. They require further elucidation. They are in groups each containing three or four glands, as illustrated in Fig. 19. Summary, The galls are all of a comparatively simple type, for while there is considerable proliferation in the tissues there is little differentiation. The medullary rays and vascular bundles respond the most readily to the gall stimulus, yet
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectgallsbo, bookyear1912
