. Botany of the living plant. Botany. Fig. 265 bis. Emhiyos ot Selaginella dentictdata, aiterBruchmaim. £/= suspensor. iCf/=root. /= foot. &6= basal wall. /:—hypocotyl. 5= apex. ^, A, ^ cotyledons, ^^ligule, (After Bruchmann.) formation of four spores from each tetrad. The microspores in each case are shed on rupture of the sporangial wall. In the ovule, as in the megasporangium of Selaginella a tetrad-division leads up to the formation of the megaspore. In both cases only one spore-mother- cell as a rule undergoes the division, but in both cases there may occasionally be more than one. In
. Botany of the living plant. Botany. Fig. 265 bis. Emhiyos ot Selaginella dentictdata, aiterBruchmaim. £/= suspensor. iCf/=root. /= foot. &6= basal wall. /:—hypocotyl. 5= apex. ^, A, ^ cotyledons, ^^ligule, (After Bruchmann.) formation of four spores from each tetrad. The microspores in each case are shed on rupture of the sporangial wall. In the ovule, as in the megasporangium of Selaginella a tetrad-division leads up to the formation of the megaspore. In both cases only one spore-mother- cell as a rule undergoes the division, but in both cases there may occasionally be more than one. In Seed-Plants usually only one megaspore, or embryo-sac, is matured. In Selaginella commonly four, and occasionally more ; but sometimes two, or even only one. Thus in point of origin, in manner of production and sometimes in number, the megaspore corresponds to the embryo-sac. The differ- ence lies in the fact that in Selaginella the megaspore, with its thick protective wall, is shed on rupture of the megasporangium ; in Seed- Plants the megaspore, or embryo-sac, is retained within the nticellus. The embedded sac is thus able to obtain continued nourishment. The biological advantage thus gained offers a ready explanation of. 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. , limited
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectbotany, bookyear1919
