Lectures on the physiology of plants . as it were cut off, furthercell-divisions occur in the remaining cells which constitute together, so to speak, areduced antheridium. This is well seen in I): each of these small cells gives rise toan antherozoid of very simi)le form, just as in the Mosses. Reluming to the germinating macrospore again, it is to be noticed that the 750 LECTURE XLII. true prothallus is separated off from the large spore-cavity by the diaphragm d d: inthis cavity there arises a large-celled tissue, such as we shall meet with later in theembryo-sac of flowering plants—the so-c
Lectures on the physiology of plants . as it were cut off, furthercell-divisions occur in the remaining cells which constitute together, so to speak, areduced antheridium. This is well seen in I): each of these small cells gives rise toan antherozoid of very simi)le form, just as in the Mosses. Reluming to the germinating macrospore again, it is to be noticed that the 750 LECTURE XLII. true prothallus is separated off from the large spore-cavity by the diaphragm d d: inthis cavity there arises a large-celled tissue, such as we shall meet with later in theembryo-sac of flowering plants—the so-called Endosperm. Figure /, then, shows at/ a young embryo, developed from a fertilised oosphere, and at e one already furtherdeveloped, the shoot portion of which (only roughly indicated) has bored into theendosperm tissue, but which subsequently grows out from it again. In order to proceed hence to the formation of the seed in the Coniferae, we needonly assume that the macrospore does not open at all, the prothallium and endosperm. Fig. 435.—Germination of Setaginella (after Pfeffer). /—/// .? Marlensu, 1 — D S <,!:,Us tiisI lonffitudinal section of a macrospore filled with prothallus and endosperm (<r aiapnragm) m wmcntwo embryos e e are developing. // a young archegonium, not yet opened. /Jl an archegoniumcontaining a fertilised oospore, which has undergone one division. A a microspore, showing thedivisions of the contents. B C different views of these divisions. D mother-cells of antherozoids, inthe mature antheridium. arising in its interior, and one or two embryos becoming developed. Of course, inthe case of the Conifer® and all Gymnospermous plants, what actually occurs is notonly what has just been mentioned, but moreover the macrospore itself also in whichthese processes occur remains lying in the very massively developed sporangium, andno opening of any kind exists through which antherozoids for instance could penetrateto the oosphere. Here, in fact, we
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectplantph, bookyear1887
