. The classification of flowering plants. Plants. 168 FLOWERIXG PLANTS [CH. longitudinal; this is followed successively by transverse and periclinal divisions, the latter marking the dermatogen of the Fig. 74. A. Optical section through the ovule of the Shepherd's Purse {Capsella); F, funicle; 3/, micropyle; E, embryo. B. Stages in the development of the embryo. 1. Suspensor, bearing below the undivided embryo-cell. 2. The embryo ( excluding the stalk or suspensor) consists of eight cells—of which four are shewn. 3. The primary epidermis has appeared: h is the hypophysis, the
. The classification of flowering plants. Plants. 168 FLOWERIXG PLANTS [CH. longitudinal; this is followed successively by transverse and periclinal divisions, the latter marking the dermatogen of the Fig. 74. A. Optical section through the ovule of the Shepherd's Purse {Capsella); F, funicle; 3/, micropyle; E, embryo. B. Stages in the development of the embryo. 1. Suspensor, bearing below the undivided embryo-cell. 2. The embryo ( excluding the stalk or suspensor) consists of eight cells—of which four are shewn. 3. The primary epidermis has appeared: h is the hypophysis, the last cell of the suspensor. 4. The primary vascular cylinder (shaded) has appeared : the hypophysis has divided, part goes to complete the embryo. 5. 6. Older stages: 6, with well-formed cotyledons (C). From Darwin. But very various departures from this simple type have been described. Thus in the single order Leguminosae Guignard^^ noted the following variations in the structure of the suspensor. In some cases it is rudimentary, consistingr only of three to four superposed cells, in others (tribe Vicieae) of two pairs of cells each with several nuclei, in others it forms a typical cell-thread, or a row of cell-pairs, or an elongated cell-body more or less distinct from the embryo (Medicago, Phaseolus), or an ovoid mass of cells. A massive suspensor has also been described in Tropaeolum. As regards the function of the suspensor, whereas in some cases it seems to be merely an attaching organ for the embryo, in the great majority it is directly or indirectly concerned with the nutrition of the developing embryo. Thus in the single large suspensorial cell typical of Monocotyledons the nucleus often attains a remarkable size, suggesting an active nutritive function, while the thread-like suspensor of Dicotyledons serves. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectplants, bookyear1904
