. Botany for high schools. Botany. 366 GENERAL MORPHOLOGY OF PLANTS. len tube makes its way into the neck end of an egg case, and empties the cells and sperms into the cytoplasm of the egg (fig. 359). The larger sperm (which was in advance in the pollen tube) unites with the egg nucleus, and without any resting stage the fer- tilized egg nucleus at once divides into two, and these into two more. These four nuclei move to the base of the egg case, and there by suc- cessive divisions organize the embryo, which is Fig. 36c. , ^ Pine seed, section pushcd dowu into the mass of the endosperm by rema
. Botany for high schools. Botany. 366 GENERAL MORPHOLOGY OF PLANTS. len tube makes its way into the neck end of an egg case, and empties the cells and sperms into the cytoplasm of the egg (fig. 359). The larger sperm (which was in advance in the pollen tube) unites with the egg nucleus, and without any resting stage the fer- tilized egg nucleus at once divides into two, and these into two more. These four nuclei move to the base of the egg case, and there by suc- cessive divisions organize the embryo, which is Fig. 36c. , ^ Pine seed, section pushcd dowu into the mass of the endosperm by remains of^nuTeUus; Certain of its cclls in the rear, which elongate femaie^gfmTto^iSytey; rapidly and are called the suspensor. The seed emh, embrvo = young • • i ^ 1 • ^ r i sporophyte'. Seed coat Hpeus m late summcr and consists of the seed malns^ofoM ^oro- coats (coats of the ovulc), the remnants of the nucellus, the endosperm and embryo with its rudimentary root, stem and leaves. In the germination of the seed (paragraph 13) and establishment of the young pine plant the life history is completed. OTHER GYMNOSPERMS.* 531. The Cycads.—The other most prominent class of the Gymnosperms is made up of the cycads (order Cycadales). These are mostly tropical or subtropical plants, but some are often grown in greenhouses, especially the Cycas revoluta, sometimes incorrectly called sago palm | on account of its trunk and large spreading leaves at the apex, giving it the aspect of the tree palms, and because of a coarse starchy material obtained from the stem called Japanese sago. Some of the cycads like Zamia (there are several species in Florida) have tuberous-like trunks. The leaves are large, stiff and feather-like because of their narrow, pinnate divisions, and resemble the leaves of some of the tree ferns. In their fructification they bear a striking resemblance to the ferns, and stand lower in grade of classification than the conifers. * For special assignment or reference
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectbotany, bookyear1910
