. Heredity and evolution in plants. Heredity; Plants. THE EVOLUTION OF PLANTS 205 bearing pollen-sacs, and the megasporophylls, bearing, not merely megasporangia, but true seeds. The ovule has a pollen-chamber, like the cycads, except that it projects a bit through the micropyle, and, strange as it may seem, fossil pollen-grains have been discovered, well preserved within this chamber. The seeds, about 3-^ inch long, have been described as resembling little acorns, enclosed like hazelnuts in smaller glandular cupules (Fig. 89). They are similar to those of the cycads, except that they are not
. Heredity and evolution in plants. Heredity; Plants. THE EVOLUTION OF PLANTS 205 bearing pollen-sacs, and the megasporophylls, bearing, not merely megasporangia, but true seeds. The ovule has a pollen-chamber, like the cycads, except that it projects a bit through the micropyle, and, strange as it may seem, fossil pollen-grains have been discovered, well preserved within this chamber. The seeds, about 3-^ inch long, have been described as resembling little acorns, enclosed like hazelnuts in smaller glandular cupules (Fig. 89). They are similar to those of the cycads, except that they are not known to have organized an embryo with cotyle-. FiG. 8g.—Restoration of a seed of Lyginodendron oldhamium (Lagenos- tema Lomaxi), from a model by H. E. Smedley. (After Scott.) dons and caulicle. Instead, the tissues of the female gametophyte only are so far found, retained within the megasporangium, which is enclosed in the integument. In this connection it is of interest to note that the seeds of some modern plants (, orchids) do not possess differ- entiated embryos, but whether this is a primitive or a reduced character is not certain. The pollen was formed in spindle-shaped pollen-sacs, having two chambers, and borne in clusters of four to six on the under side of little oval discs, from 2 to 3 millimeters long. These structures. 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 Gager, C. Stuart (Charles Stuart), 1872-1943. Philadelphia, P. Blakiston's Son & Co.
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectplants, bookyear1920
