. The anatomy of woody plants. Botany -- Anatomy. CONIFERALES 337 has been demonstrated in earlier pages that Paleozoic gymno- sperms are characterized by the complete absence of parenchyma- tous elements in the wood and at the same time by the general absence of annual rings in the stem. Pinus, as regards the organ- ization of the storage devices of the wood, is therefore clearly allied with Paleozoic types such as the Cordaitales. There are other conditions, however, which indicate for Pinus a primitive position among the Abietineae. First of all there is the possession of short-shoots. Pinu
. The anatomy of woody plants. Botany -- Anatomy. CONIFERALES 337 has been demonstrated in earlier pages that Paleozoic gymno- sperms are characterized by the complete absence of parenchyma- tous elements in the wood and at the same time by the general absence of annual rings in the stem. Pinus, as regards the organ- ization of the storage devices of the wood, is therefore clearly allied with Paleozoic types such as the Cordaitales. There are other conditions, however, which indicate for Pinus a primitive position among the Abietineae. First of all there is the possession of short-shoots. Pinus in this feature of organiza- tion presents a marked resemblance to the Ginkgoales, which. FIG. 245.—Microspores of Ginkgo and Abies also bear their foliar organs on special spurs or short-shoots. Nor is the common possession of short-shoots unparalleled by other significant characteristics. Ginkgo and the Abietineae strongly resemble one another in the possession of bisporangiate sporo- phylls. In the two groups there are two microsporangia and two megasporangia or seeds on the reproductive foliar organs. The view sometimes advanced that the ovuliferous scales in the Abietineae consist of a fused pair of foliar structures has apparently no evidence in its favor. It is as clearly a single leaf as is the microsporophyll. The microspores in the Abietineae and in the Ginkgoales also present striking points of resemblance which have only recently been completely realized. In the monotypic Ginkgo the pollen is winged as in the more primitive Abietineae and resembles in its internal organization the structures found in the microspores of that subtribe of conifers. Fig. 245 illustrates the numerous features of internal and external resemblance between. 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 Jeffrey, Edw
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