. Botany of the living plant. Botany. 312 BOTANY OF THE LIVING PLANT the apex of the prothallus (Fig. 254, C). Meanwhile its generative cell has divided to form a stalk-cell and a body-cell. The former breaks away from its attachment, and the contents of the grain enter the tube. The body-cell divides during transit to form the tu'o male gametes. Thus provided, the tube enters the neck of an archegonium, and the gametes are transferred into the ovum. The nucleus of one of the gametes fuses with the nucleus of the ovum. The result of the fusion. Fig. :;.s4. Pic^a vulgaris. A âlongitudinal secti
. Botany of the living plant. Botany. 312 BOTANY OF THE LIVING PLANT the apex of the prothallus (Fig. 254, C). Meanwhile its generative cell has divided to form a stalk-cell and a body-cell. The former breaks away from its attachment, and the contents of the grain enter the tube. The body-cell divides during transit to form the tu'o male gametes. Thus provided, the tube enters the neck of an archegonium, and the gametes are transferred into the ovum. The nucleus of one of the gametes fuses with the nucleus of the ovum. The result of the fusion. Fig. :;.s4. Pic^a vulgaris. A âlongitudinal section througii apex oi female prothallus, and one archegonium. n = neck. i',cc=ventral canal cell, oi' âovum. £ âneck seen from above. C~entry of pollen-tube with gametes into the canal of the arche- gonium. i-i â ' 100 ; B, C y 250.) {-^fter Strashurger.) is the zygote. Both the ovum and the male gamete were haploid, and the consequence of their fusion is to initiate the new diploid phase, which forms the embryo. The process is variable in dilTerent genera of Conifers, and rather complicated. In Piniis and its allies the nucleus of the zygote divides at once, first into two and then into lour. The resulting nuclei sink to the base of the egg. lying in a single plane. Divisions follow to foriu lour tiers consisting of four cells each (Fig. 255). Of these the lowest but one elongate as the suspensors (s); the lowest form the embryonic tier [e]. In the Pines these may either form togetlier a single embryo, or they may separate, each borne on its own suspensor, and so foul" embryos may result Irom one fertilisation. As there are se\'eral archegonia, and each may be fertilised, a degree of polyembryony is possible. As a rule one embryo in each ovule secures the ascendency over the. 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 perfec
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectbotany, bookyear1919
