Elementary botany . Fig. ovule (macrosporangium) of podophyllum, n, nucellus containing the one-celled stage of the macrospore; , inner integument; , outer integument. times until eight are formed, four in the micropylar end of theembryo sac and four in the opposite end. In some plants ithas been found that one nucleus from each group of four movestoward the middle of the embryo sac. Here they fuse togetherto form one nucleus, the endosperm nucleus or definitive nucleusshown in fig. 390. One of the nuclei at the micropylar end isthe egg, while the two smaller ones nearer th
Elementary botany . Fig. ovule (macrosporangium) of podophyllum, n, nucellus containing the one-celled stage of the macrospore; , inner integument; , outer integument. times until eight are formed, four in the micropylar end of theembryo sac and four in the opposite end. In some plants ithas been found that one nucleus from each group of four movestoward the middle of the embryo sac. Here they fuse togetherto form one nucleus, the endosperm nucleus or definitive nucleusshown in fig. 390. One of the nuclei at the micropylar end isthe egg, while the two smaller ones nearer the end are the syner- 328 MORPHOLOG Y. gids. The egg cell is all that remains of the archegonium inthis reduced prothallium. The three nuclei at the lower endare the antipodal Fig. peltatum, ovule containing mature embryo sac; two synergids andeggs at left, endosperm nucleus in center, three antipodal cells at right. 655. Embryo sac is the young female prothallium.—In are shown the different stages in the development of the embryo sac in lilium. Theembryo sac at this stage is theyoung female prothallium, andthe egg is the only remnant of thefemale sexual organ, the arche-gonium, in this reduced gameto-phyte. 656. Fertilization.—When thepollen tube has reached the em-bryo sac (paragraph 652) it opensMacrospore (one-ceiled stage) of lilium. anci tne two sperm cells are emptiednear the egg. The first sperm nucleus enters the protoplasmsurrounding the egg nucleus and uniting with the latter bringsabout fertilization. The second sperm nucleus often uniteswith the endosperm nucleus (or with one or both of the polarnuclei), bringing about what some call a second this takes place in addition to the union of the fi
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Keywords: ., bookauthoratk, bookcentury1900, bookdecade1900, booksubjectbotany
