. Morphology of gymnosperms. Gymnosperms; Plant morphology. 298 MORPHOLOGY OF GYMNOSPERMS •gigantea. Among the Cupressineae the range is two to five, two being usual in Thuja, Callitris, Widdringtonia, and Actinostrohus; two or three in Libocedrus; and the whole range of two to five in the various species of Juniperus and Cupressus. Among the Araucarineae, Agathis has two cotyledons, and Araucaria two to four. These num- bers will doubdess vary upon wider acquaintance with the forms, but they serve to illustrate that the fluctuations occur not only between tribes, but also within tribes and ge
. Morphology of gymnosperms. Gymnosperms; Plant morphology. 298 MORPHOLOGY OF GYMNOSPERMS •gigantea. Among the Cupressineae the range is two to five, two being usual in Thuja, Callitris, Widdringtonia, and Actinostrohus; two or three in Libocedrus; and the whole range of two to five in the various species of Juniperus and Cupressus. Among the Araucarineae, Agathis has two cotyledons, and Araucaria two to four. These num- bers will doubdess vary upon wider acquaintance with the forms, but they serve to illustrate that the fluctuations occur not only between tribes, but also within tribes and genera, and even Figs. 367, 368.—Araucaria brasiliana: a proembryo filling the entire egg; only the shaded cells belong to the embryo proper, the wedge-shaped mass of cells below being the embryo cap; fig. 368, later stage, showing the wedge-shaped mass of cells being thrust aside; X1S3.—After Strasetirger (25). The explanation of this variation is difficult, but there seem to be two alternatives: either the polycotyledonous condition is derived from the splitting of two ancestral cotyledons (141, 154), or the dicotyle- donous condition is derived from the fusion of more numerous cotyledons. In other words, it is a question whether polycotyledony is primitive or derived. The argument for the derivation of polycotyledony from dicotyle- dony has been developed by Hill and De Fealne (141, 154). This belief dates from Adanson and Jussleu, and was supported by. 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; Chamberlain, Charles Joseph, b. 1863; Coulter, John Merle, 1851-1928. Morphology of spermatophytes. Part I. Gymnosperms. Chicago, University of Chicago Press
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