. Fecundation in plants. Plant embryology; Plants, Sex in; Karyokinesis. Fig. 20.—Fusion of gametes in Spiro^yra. A, portion of two conjugating filaments of Spirogyra quinina.—(After Strasburger,)- B, young zygote provided witli only a tliin wall. C, zygote at a later stage; the cell-wall is thicker, and the nuclei have united, but the nucleoli have not fused. has not beoi demonstrated, however, and it is highly probable that we have to do here with an active plasmic movement operating under the chemotactic stimulus of the two protoplasts. Here fecundation con- sists in the union of the entire
. Fecundation in plants. Plant embryology; Plants, Sex in; Karyokinesis. Fig. 20.—Fusion of gametes in Spiro^yra. A, portion of two conjugating filaments of Spirogyra quinina.—(After Strasburger,)- B, young zygote provided witli only a tliin wall. C, zygote at a later stage; the cell-wall is thicker, and the nuclei have united, but the nucleoli have not fused. has not beoi demonstrated, however, and it is highly probable that we have to do here with an active plasmic movement operating under the chemotactic stimulus of the two protoplasts. Here fecundation con- sists in the union of the entire plasma of both gametes, though DeBary records the case of Sfirogyra heeriana^ in which a small vesicle of plasma is left beyond the partition wall in the conjugation canal. Concerning the behavior of the chlorophyll bands in the zygote, much diversity of opinion exists. DeBary ('58) and Schmitz ('82) observed that in species with one chlorophyll band the two chloro- plasts united in the zygote to form one continuous band. Overton ('88), on the contrary, asserts that the single band of the female gamete segments at the middle during the fusion of the protoplasts; the two halves then separate, and each piece unites with the ends of the band ^ See Fig. lo, p. 17, Die Natiirlichen Pflanzenfamilien, x Theil, 2 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 Mottier, David Myers. [Washington] The Carnegie Institution of Washington
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