. Botany of the living plant. Botany; Plants. 496 BOTANY OF THE LIVING PLANT A vertical section through the sorus of Dryopteris shows an enlarged receptacle, traversed by the vascular strand. The indusium rising from it overarches the numerous sporangia which are attached basally by long thin stalks (Fig. 387). The head of each sporangium is. Fig. 388. Successive young stages in the segmentation of the sporangium of Dryopteris Filix-mas. (After Kny.) shaped like a biconvex lens ; its margin is almost completely sur- rounded by a series of indurated cells, which form the mechanically effective
. Botany of the living plant. Botany; Plants. 496 BOTANY OF THE LIVING PLANT A vertical section through the sorus of Dryopteris shows an enlarged receptacle, traversed by the vascular strand. The indusium rising from it overarches the numerous sporangia which are attached basally by long thin stalks (Fig. 387). The head of each sporangium is. Fig. 388. Successive young stages in the segmentation of the sporangium of Dryopteris Filix-mas. (After Kny.) shaped like a biconvex lens ; its margin is almost completely sur- rounded by a series of indurated cells, which form the mechanically effective annulus. This stops short on one side, where several thin- walled cells define the stomium, or point where dehiscence will take place (Figs. 387, 389, 4a). Within are the dark-coloured spores, which on opening a ripe sporangium carefully in a drop of glycerine may be counted to the number of 48. Normally the sporangia open in dry air, and the dry and dusty spores are forcibly thrown Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Bower, F. O. (Frederick Orpen), 1855-1948; Wardlaw, C. W. (Claude Wilson), 1901-. London, Macmillan and Co. , ltd.
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