. Fecundation in plants. Plant embryology; Plants, Sex in; Karyokinesis. 176 ANGIOSPERMS. embryo-sac and can be distinctly recognized, no trace of the cytoplasm which accompanied them in the tube can be distinguished, so that the exact behavior of this cytoplasm is unknown. Consequently we are concerned here solely with the union of the nuclei. THE FUSION OF MALE AND EGG-NUCLEI. We shall follow first the male nucleus which fuses with that of the egg-cell. It is presumably the first male nucleus which escapes from the pollen tube that unites with the nucleus of the egg, but positive proof on th
. Fecundation in plants. Plant embryology; Plants, Sex in; Karyokinesis. 176 ANGIOSPERMS. embryo-sac and can be distinctly recognized, no trace of the cytoplasm which accompanied them in the tube can be distinguished, so that the exact behavior of this cytoplasm is unknown. Consequently we are concerned here solely with the union of the nuclei. THE FUSION OF MALE AND EGG-NUCLEI. We shall follow first the male nucleus which fuses with that of the egg-cell. It is presumably the first male nucleus which escapes from the pollen tube that unites with the nucleus of the egg, but positive proof on this point is want- ing. In certain spe- cies of Liliutn, and various observers have shown this to be true of many other Angiosperms, the male nucleus, when observed in the egg- cell, is frequently sausage-shaped, worm-like, or S- shaped (Mottier, '97), making one or more spiral-like turns, which is sug- gestive of a worm- like motion, but posi- tive proof of anysuch movement is want- ing. It applies itself to the nucleus of the egg, retaining the form mentioned for some time (Fig. 74, A). The structure of the two sexual nuclei at this stage is accurately shown for Lilium Tnartagon in this figure. The two nuclei are in the resting condition, although the chromatin of the male nucleus is a little more regularly arranged. The male nuclei when in the embryo-sac stain a deeper red, safranin, gentian violet and orange G being used, than the other nuclei of the sac, and for that reason they may be readily recognized. As fusion progresses, the nuclei become quite alike in shape, size and structure (Fig. 74, B). Their membranes gradually disappear at the place of contact, their cavities become one, and the resulting fusion nucleus, which is in the. Fig. 74;—Fusion of sexual nuclei. A, vermiform male nucleus applied to egg-nucleift, Lilium martagon. B, egg-cell ofZt7i«wfaMt/2V«w, showing sexual nuclei in act of fusing; the nuclear membranes have disappeared at place of Pleas
Size: 1596px × 1565px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, bookpublisherwashi, bookyear1904
