. The origin of a land flora, a theory based upon the facts of alternation. Plant morphology. SPORE-PRODUCING MEMBERS 417 abaxial loculus which will be thus traversed. ' A truly radial section of a young synangium is shown in Fig. 232 b, the arrow indicating the direc- tion of the main axis : the cell ( x ) is a conical cell, which is commonly though perhaps not constantly found occupying the centre of the apical surface of the synangium. The cell shaded is believed to be the arche- sporial cell for one of the loculi, but after comparison of a large number ABC. Fig. 232. Psilotitm triq-uetrum,
. The origin of a land flora, a theory based upon the facts of alternation. Plant morphology. SPORE-PRODUCING MEMBERS 417 abaxial loculus which will be thus traversed. ' A truly radial section of a young synangium is shown in Fig. 232 b, the arrow indicating the direc- tion of the main axis : the cell ( x ) is a conical cell, which is commonly though perhaps not constantly found occupying the centre of the apical surface of the synangium. The cell shaded is believed to be the arche- sporial cell for one of the loculi, but after comparison of a large number ABC. Fig. 232. Psilotitm triq-uetrum, Sw. Various stages of development of the synangium and sporangium. In C the sporogenous group is shaded. D shows the differentiation of its cells, the fertile cells being shaded. K shows the disorganisation of the remaining cells without forming spores. X100. of sections I am still uncertain whether the whole of the sporogenous tissue in each loculus is really referable to a single parent cell, for just the same difficulty arises here as in Tmesipteris in recognising the exact limits of the sporogenous masses. The subsequent stages of development are illustrated by Figs. 232 c, d, e, and it will be seen from these how the sporogenous masses assume large dimensions, and are at first composed of uniform cells. The wall of the synangium meanwhile becomes multiseriate, and the cells of the outermost layer assume a deep and prismatic form, while the inner layers are narrow. 2D. 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. London, Macmillan and Co. , Ltd.
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