Elementary botany . 359. At the sametime the two cells which were formed inthe pollen grain (antheridium) from thecentral cell move down into the tube. Oneof these is the generative cell, or bodycell, and the other is called the stalk cell,though it is more properly a sterile half ofthe central cell. The nucleus of the gener-ative cell, about the time the archegoniumis mature, divides to form two nuclei,which are the sperm nuclei, and the onein advance is the larger, though it is muchsmaller than the egg nucleus. 625. Fertilization.—Very soon after thearchegonia are mature (early in June in th
Elementary botany . 359. At the sametime the two cells which were formed inthe pollen grain (antheridium) from thecentral cell move down into the tube. Oneof these is the generative cell, or bodycell, and the other is called the stalk cell,though it is more properly a sterile half ofthe central cell. The nucleus of the gener-ative cell, about the time the archegoniumis mature, divides to form two nuclei,which are the sperm nuclei, and the onein advance is the larger, though it is muchsmaller than the egg nucleus. 625. Fertilization.—Very soon after thearchegonia are mature (early in June in thenorthern United States) the pollen tubegrows through into the archegonium andempties the two sperm nuclei, the vegetativenucleus and the stalk cell, into the proto-plasm of the large egg. The larger of thetwo sperm nuclei at once comes in contactwith the very large egg nucleus and sinksdown into a depression of the same, asshown in fig. 361. These two nuclei, in thepines, do not fuse into a resting nucleus, but. Fig. division of the egg in the at once organize the nuclear figure for the whit? pif cutting off the ventral canal cell at the apex of the first division of the thus formed, and these dfour nuclei which sink to the bottom of the archegonium and there organ- Two nuclei archegonium. End, endospermare thus formed, and these divide to form ArB* arche^onium 5o8 MORPHOLOGY. ize the embryo which pushes its way into the endosperm from which itderives its food (fig. 362). 626. Homology of the parts of the female cone.—Opinions are divided asto the homology of the parts of the female cone of the pine. Some considerthe entire cone to be homologous with a flower of the angiosperms. The
Size: 1082px × 2310px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthoratk, bookcentury1900, bookdecade1900, booksubjectbotany
