. Nature and development of plants. Botany. DEVELOPMENT OF PLANTS 355 groups suggestive of the sori of the ferns, in some forms even showing a rudimentary annulus. There is a considerable vari- ation in the form of the sporophylls and the distribution of the sporangia. For example, in Cycas, the megasporophylls are loosely associated and only slightly modified, the sporangia being developed on their margins (Fig. 245, 35). The microsporo-. FlG. 245. Sporophylls and sporangia of the Cycads: 2, strobilus of Zamia. 2A, cross-section of strobilus of Zamia, showing arrangement of microsporo- phylls
. Nature and development of plants. Botany. DEVELOPMENT OF PLANTS 355 groups suggestive of the sori of the ferns, in some forms even showing a rudimentary annulus. There is a considerable vari- ation in the form of the sporophylls and the distribution of the sporangia. For example, in Cycas, the megasporophylls are loosely associated and only slightly modified, the sporangia being developed on their margins (Fig. 245, 35). The microsporo-. FlG. 245. Sporophylls and sporangia of the Cycads: 2, strobilus of Zamia. 2A, cross-section of strobilus of Zamia, showing arrangement of microsporo- phylls. 2S, microsporophyll enlarged, showing sporangia arranged in sori. 2C, sorus of three sporangia that have opened. 2D, microsporophyll of Cycas. 3, cross-section of a strobilus of Zamia, showing arrangement of megasporophylls. 3^!, megasporophyll enlarged with two sporangia. The one on the right shown in section; ms, megaspore; i, integument; sp, spor- angium; m, micropyle. 35, megasporophyll of Cycas with laterally ar- ranged megasporangia.—H. O. Hanson. phylls are small and more compactly arranged, the sporangia being associated in sori on the lower surface of the sporophylls (Fig. 245, 2D). In Zamia, the strobili and sporophylls are quite suggestive of Equisetum, the sporangia being developed on the inner side of shield-like sporophylls (Fig. 245, 2-2,A).- The microspores originate by the division of certain cells just beneath the epidermis and are discharged from the sporangium very much as in the Ophioglossales. The megasporangia,. 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 Curtis, Carlton Clarence, 1864-1945. New York, H. Holt
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