. Text-book of botany, morphological and physiological. Botany. FILTCINEJE. 471 and in the mode of its development, it shows a still greater resemblance to the tissue that fills up the embryo-sac of Gymnosperms, and even of Angiosperms, In Isoetes the cavity begins to be filled with cellular tissue a few weeks after the escape of the macrospores from the decaying macrosporangium; the cells of this tissue are all at first naked (without cell-wall); they appear to become enclosed in firm cell-walls only when the whole cavity of the endospore is filled with them (Fig, 330). In the meantime the en
. Text-book of botany, morphological and physiological. Botany. FILTCINEJE. 471 and in the mode of its development, it shows a still greater resemblance to the tissue that fills up the embryo-sac of Gymnosperms, and even of Angiosperms, In Isoetes the cavity begins to be filled with cellular tissue a few weeks after the escape of the macrospores from the decaying macrosporangium; the cells of this tissue are all at first naked (without cell-wall); they appear to become enclosed in firm cell-walls only when the whole cavity of the endospore is filled with them (Fig, 330). In the meantime the endospore thickens, becomes differentiated into layers, and assumes a finely granular appearance, phenomena which, as Hofmeister insists, are exhibited in like manner in the embryo-sacs of Coniferse. The spherical pro-. FIG of Selaginella (after Pfeffer); /-///, S. Martensii, A-V, 5. caulescent; /longitudinal section of a macrospore filled with the prothallium and 'endosperm,' d the diaphragm, e *'two embryos in process of formafcon, // a young archegonium not yet open; ///an archegonium with the oospore fertilised and divided once:; -rf a microspore showing the primordial cells; B C different views of these divisions; D the mother-cells of the antherozoids in the perfect ^ antheridium; v, vegetative cell. thallium now swells up, the three convergent edges of the exospore burst length- wise and thus form a three-rayed fissure, where the prothallium is covered only by the membranous endospore; this also peels off, and softens, finally exposing the corresponding part of the prothallium. At its apex appears the first^ arche- gonium ; if this is not fertilised, several others are subsequently formed at its side. In Selaginella, even when the macrospores are still lying in the sporangium, the apical region is found to be clothed with a small-celled meniscus-shaped mass of tissue which is probably formed, during the ripening of the spores, by the division. Please note
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectbotany, bookyear1882
