. Fecundation in plants. Plant embryology; Plants, Sex in; Karyokinesis. io6 FECUNDATION ; HETEROGAMETKS. together with a small quantity of protoplasm, is liberated, and so comes to lie in the peripheral part of the egg. The cell-wall of the oosphere is then completed, and the end of the fertilization-tube remains firmly attached to ; Although the presence of the male nucleus, while in the periphery of the egg, was not clearly demonstrated, yet this is not absolute proof to the contrary. " I have," Trow continues, " satisfied myself, however, of the presence of two nucle
. Fecundation in plants. Plant embryology; Plants, Sex in; Karyokinesis. io6 FECUNDATION ; HETEROGAMETKS. together with a small quantity of protoplasm, is liberated, and so comes to lie in the peripheral part of the egg. The cell-wall of the oosphere is then completed, and the end of the fertilization-tube remains firmly attached to ; Although the presence of the male nucleus, while in the periphery of the egg, was not clearly demonstrated, yet this is not absolute proof to the contrary. " I have," Trow continues, " satisfied myself, however, of the presence of two nuclei in the egg at all times in this stage, one peripheral and one central, and the periphe^ral one always close to the point of attachment of the ;. Fig. 38.—Young stages of two oo^onia and two egg-cells oi A. americana var, cambrica,—(After Irow.) A, section of young stage before delimination from hypha, showfng cytoplasmic structure and nuclei. Bj median section at stage preceding balling ;/'.£. n., female gamete nuclei; deg. n., degenerate nuclei. C, egg containing one nucleus; apex of conjugation-tube con- taining male nucleus has penetrated egg, D, egg Trom a 5-day culture, in which the two gamete nuclei are in contact; m, g. n., male gamete nucleus. At a later stage obtained from a five-day culture the two nuclei are found applied to each other in the center of the egg (Fig. 38, D). They are in the resting condition, and about the same size, the male being distinguished from the female only by its smaller nucleolus. From the fact that the sexual nuclei were found side by side in a five- day culture, and from an examination of many hundreds of oospores from six- to eight-day cultures, it is inferred that about three days are required for the complete fusion, during which time the nuclei remain in the resting condition, a phenomenon of frequent occurrence among thallophytes. In the oospores of nine- or ten-day cultures, which have developed a well
Size: 1799px × 1389px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, bookpublisherwashi, bookyear1904
