. Botany for high schools and colleges. Botany. (/ YMNOSPERM^. 403 iogue of a macrospore, which here is not freed from the parent plant. The endosperm clearly bears the same rela- tion to the embryo sac as the prothallium of Isoetes does to the-macrospore f and the corpuscula are slightly modified archegonia. In some corpuscula the resemblance to arche- gonia is very marked, the germ-cell below being surmounted by a short neck; Strasburger has even discovered a rudi- mentary axial-cell, thus completing the correspondence of these organs to those of the higher Pteridophytes. 512;—Fertilization
. Botany for high schools and colleges. Botany. (/ YMNOSPERM^. 403 iogue of a macrospore, which here is not freed from the parent plant. The endosperm clearly bears the same rela- tion to the embryo sac as the prothallium of Isoetes does to the-macrospore f and the corpuscula are slightly modified archegonia. In some corpuscula the resemblance to arche- gonia is very marked, the germ-cell below being surmounted by a short neck; Strasburger has even discovered a rudi- mentary axial-cell, thus completing the correspondence of these organs to those of the higher Pteridophytes. 512;—Fertilization is eflect- ed by means of the pollen, which comes in contact with the apex of the ovule. It is transported from the male flowers mostly by the wind, which accounts for the im- mense quantity produced. When the ovule has reached the proper stage the micropyle is filled with a fluid, which, dry- ing, cai'ries the adherent pollen grains into contact with the apex of the ovule body, where they germinate and form pol- len tubes ; the latter penetrate puscuium; p, two poiien grains ap- ,T ni J • J. Ji 1 T plied to the apex of the ovule body, the soft tissue OI the ovule and fnto which they have sent two pollen eventually reach the corpus- tubes,«, ».-Afterp,anti. cula (Fig. 299). In those cases where the corpuscula are separated from one another each pollen tube comes in con- tact with only one corpusculum (Figs. 397, B, and 399) ; but when the corpuscula are close together a single pollen tube may come in contact with all of them (Fig. 398, 1 and 2). The union of the protoplasm of the pollen tube with that of the germ-cell appears to take place by diffusion through the wall of the former, as no openings in it have been discovered. After fertilization the protoplasm in the germ-cell becomes more turbid and granulnr, and soon at the base a transverse partition is formed, cutting off a cell, which is the rudiment. Fig. 399.—Diagrammatic i-cction of an ovule of Pinvs, showing fe
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectbotany, bookyear1885
