. Plant studies; an elementary botany. Botany. SPEEIIATUPIIYTES : (iYMN()Sl>EUMK 551 nc pine the micropyle is directed downward, toward the base of the sporophyll. 230. The gametophytes.—The male and female gameto- phytes are so small that they develop entirely within the spores (pollen-grain and embryo-sac), and there- fore can only be observed by the microscope. The female gameto- phyte (often called " en- dosperm ") fills up the large embryo-sac, and on its surface toward the micropyle develojos regu- lar flask-shaped arcbe- gonia (Fig. 312). The male gameto- phyte is still mor
. Plant studies; an elementary botany. Botany. SPEEIIATUPIIYTES : (iYMN()Sl>EUMK 551 nc pine the micropyle is directed downward, toward the base of the sporophyll. 230. The gametophytes.—The male and female gameto- phytes are so small that they develop entirely within the spores (pollen-grain and embryo-sac), and there- fore can only be observed by the microscope. The female gameto- phyte (often called " en- dosperm ") fills up the large embryo-sac, and on its surface toward the micropyle develojos regu- lar flask-shaped arcbe- gonia (Fig. 312). The male gameto- phyte is still more re- duced, and is represented by a very few small cells which apj^ear within the piollen - grain, two of which are sperm - cells. These sperm-cells must reach the archegonia, and accordingly the pol- len-grain sends out a tube {pollen-tulie)^ into which the sperm-cells enter, and are thus brought to the archegonia (Fig. 110). 231. Fertilization. — Before fertilization can take place the pollen-grains (microspores) must be brought as near as possible to the female gaiuotophyte with its arche- gonia. The spores are formed in very great Flu. 312. Diagrammatic sectinn tlironyli o\'u]e (niegasporangiiim) of spruce iPicea), sliowing intecjnment (?), nuccllas inc), endosperm or female gametophyte (e) which fills the large mcgaspore imbedded in the nucellus, two arelifgnnia (a) with short neck ic) and venter containing the egg (o), and position of ger- minating pollen-grains or microspores ip) whose tnhcs (0 penetrate the nueelhis tissue and reach the archegonia.—After 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 perfectly resemble the original Coulter, John Merle, 1851-1928. New York, D. Appleton and Company
Size: 1252px × 1997px
Photo credit: © Central Historic Books / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, booksubjectbotany, bookyear1900
