. Lectures on the evolution of plants. Botany; Plants. 170 EVOLUTION OF PLANTS pollen-spores produced is enormously in excess of the macrospores. Indeed, so abundant is the pollen, that the ground in the neighborhood of the trees is some-. FiQ. 42 (Coniferse). — A, branch of a pine {Pinus contorta) with male flowers, ./Z; B, longitudinal section of a single flower, showing the arrangement of the sporophylls; C, a single sporophyll, showing the two microsporangia, mi, upon its lower surface; D, a section through the microsporangium; E, a single microspore, showing the antheridinm, an, and the v
. Lectures on the evolution of plants. Botany; Plants. 170 EVOLUTION OF PLANTS pollen-spores produced is enormously in excess of the macrospores. Indeed, so abundant is the pollen, that the ground in the neighborhood of the trees is some-. FiQ. 42 (Coniferse). — A, branch of a pine {Pinus contorta) with male flowers, ./Z; B, longitudinal section of a single flower, showing the arrangement of the sporophylls; C, a single sporophyll, showing the two microsporangia, mi, upon its lower surface; D, a section through the microsporangium; E, a single microspore, showing the antheridinm, an, and the vesicular outgrowths of the wall, v, which serve as sails; F, a female flower of the same pine; G, a single sporophyll from the female flower, showing the small scale, sc, by which it is subtended; H, a sporophyll from an older cone, showing two macrosporangla (ovules), ma, upon its inner face; I, longitudinal section of an ovule (macro- sporangium) ; the large macrospore contains the gametophyte, g, bearing several archegonla, ar; p,a, pollen'-8t>ore sending down the tube by which the archegonla are fertilized; J, a young embryo; sus, sus- pensor; x, apical cell; K, section of a ripe seed, containing the embryo, em, imbedded in the prothallial tissue, g; L, young sporophyte, show- ing the cotyledons, cot; stem, st; root, r; s, the empty seed-coat. times covered with a layer of the sulphur-colored powder. The germination of the pollen-spores and the fertili- zation of the archegonium are effected as in Taxus. As ill that genus, no trace of motile spermatozoids has yet. 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 Campbell, Douglas Houghton, 1859-1953. New York, London, The Macmillan company
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Keywords: ., bookcentury1900, bookdecade, booksubjectbotany, booksubjectplants
