. Fecundation in plants. Plant embryology; Plants, Sex in; Karyokinesis. 156 ARCHEGONIATES. THE ARCHEGONIUM. The development of the archegoniutn in the Cycadacece and in Ginkgo^ which is similar to that of Pinus, is too well known to require a detailed description in tliis place. The manner, however, in which the large central cell is nourished during its growth by the immediately surrounding cells of the prothallium is, if Ikeno's observations be cor- rect, a phenomenon of a rather rare occurrence in the Gymnosperms, and merits some special mention. These surrounding cells, which are separate
. Fecundation in plants. Plant embryology; Plants, Sex in; Karyokinesis. 156 ARCHEGONIATES. THE ARCHEGONIUM. The development of the archegoniutn in the Cycadacece and in Ginkgo^ which is similar to that of Pinus, is too well known to require a detailed description in tliis place. The manner, however, in which the large central cell is nourished during its growth by the immediately surrounding cells of the prothallium is, if Ikeno's observations be cor- rect, a phenomenon of a rather rare occurrence in the Gymnosperms, and merits some special mention. These surrounding cells, which are separated from the central cell by thick cellulose walls, are of a uniform size, each possessing dense cytoplasm and a large nucleus. Before the archegonium is full grown the nuclei of these cells show a fine and distinct threadwork; but, as this organ approaches maturity, the nuclei, with the exception of the nucleoli, are transformed into homo- ^ \ A â -Or. Fig, 64.âThree cells from layer of prothalUal cells immediately surrounding upper part of central cell of archegonium of Cyciis, showing protoplasmic connections between these cells ; in B the beak of nucleus extends into plasmic bridge.â(After Ikeno.) geneous and diffusely staining boc^es. This phenomenon is not confined solely to the cells forming the wall of the archegonium, but it may extend to adjacent cells of the prothallium. This nuclear change takes place only in cells near the upper part of the central cell. Goroschankin has shown that in the Cycadacece fine cytoplasmic connections exist between the central cell of the archegonium and the surrounding cells. From Ikeno's figures it seems that the cytoplasmic strands in Cycas are relatively large, and that large granular plasmic masses pass over bodily into the central cell (Fig. 64, A, B). Fre- quently the nucleus itself will send out a beak or protuberance toward the nearest plasmic connection. Arnoldi (1900) finds that in several species of Pinus and in Abies the nuc
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