. Fecundation in plants. Plant embryology; Plants, Sex in; Karyokinesis. CELL-DIVISION. 39 at a very late period strands of protoplasm are seen connecting the spore plasma with that in the columella. It is not impossible that many of the apparently disk-shaped vacuoles are sections of curved openings which burrow through the plasma from below upwards. Frequently vacuoles which are distinct in one plane are seen, by focussing up and down, to lie connected. There can be little doubt, however, that a considerable part of cleavage of the columella is accomplished by flattening and lateral fusion o
. Fecundation in plants. Plant embryology; Plants, Sex in; Karyokinesis. CELL-DIVISION. 39 at a very late period strands of protoplasm are seen connecting the spore plasma with that in the columella. It is not impossible that many of the apparently disk-shaped vacuoles are sections of curved openings which burrow through the plasma from below upwards. Frequently vacuoles which are distinct in one plane are seen, by focussing up and down, to lie connected. There can be little doubt, however, that a considerable part of cleavage of the columella is accomplished by flattening and lateral fusion of originally ellipsoidal or spheri- cal vacuoles ; that is, the cleavage is not entirely by a furrow from the plasma. Fig. 15,—Cell-cleavage in sporangium oiFiloiolut crystallimis.—(fLfta Harper.) A, median section at stage when columella is forming. B, section of spore-plasma from base of sporangium, showing surface cleavage-furrows; a, sporangial wall. C, section of portion of upper part of a sporangium, showing irregular sausage-shaped bodies formed by cleavage of spore-plasma. D, similar to C, but older, showing uninucleate masses (protospores). membrane at the mouth of the sporangiophore, but is at least in part a process of separation by excretion of a liquid into vacuoles and their fusion side by side in situ. These vacuoles are not situated on the extreme boundary of the pro- toplasm adjacent to the large central vacuole, but placed where the dense spore- plasma first becomes characteristically spongy. At the base of the sporangium indeed, they cut through plasma as dense as the densest spore-plasma of the sporangium. Why the cell-wall of the columella could not be deposited on the surface of the central vacuole, as well as on the surface of the small vacuoles,. 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 or
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