. Heredity and evolution in plants . FIG. 99.—Cycadeoidea ingens. Restoration of an expanded bispor-angiate cone, or flower, in nearly longitudinal section. Restored from asilicified fossil. (After Wieland.) bracts arranged in spirals. The bracts surrounded acampanula of about 20 stamens. Each stamen was, inreality, a pinnately compound sporophyll, about 4 incheslong, rolled in toward the center of the flower, and bear-ing two rows of compound microsporangia (pollen-sacs)on each leaflet. They thus closely resembled the sporo-phyll of a fern. 1 The staminate cones of Zamia are lateral. 2l6 HERE
. Heredity and evolution in plants . FIG. 99.—Cycadeoidea ingens. Restoration of an expanded bispor-angiate cone, or flower, in nearly longitudinal section. Restored from asilicified fossil. (After Wieland.) bracts arranged in spirals. The bracts surrounded acampanula of about 20 stamens. Each stamen was, inreality, a pinnately compound sporophyll, about 4 incheslong, rolled in toward the center of the flower, and bear-ing two rows of compound microsporangia (pollen-sacs)on each leaflet. They thus closely resembled the sporo-phyll of a fern. 1 The staminate cones of Zamia are lateral. 2l6 HEREDITY AND EVOLUTION IN PLANTS The axis of the flower terminated in a cone-shapedreceptacle, bearing the stalked ovules, and numeroussterile scales (Figs. 97 and 98). The mature seeds oftencontain the well-preserved fossil embryos, with twocotyledons which quite fill out the nucellus, and showthat there was little or no endosperm. These are char-acters never found in the lowest group of modern seed-. FIG. ico.—Cycadeoidca Dartoni. Tangential section through outertissues of the (fossilized) trunk, showing the very numerous seeds are very small (the illustration being natural size), and nearlyevery one has a dicotyledonous embryo. There were over 500 such coneson the original stem. (After a photograph loaned by Prof. Wieland.) bearing plants (the Gymnosperms), but only in thehighest group of Angiosperms, the Dicotyledons. Infact, the French paleobotanist, Saporta, called some of theCycadeoids, Proangiosperms. 145. Relation of Cycadeoidea to Modern Angiosperms. -The question of the ancestry of the Angiosperms is the most important problem of paleobotany. Although the THE EVOLUTION OP PLANTS 217 Hemicycadales possess many of the primitive anatomicalfeatures that characterize the Cycadofilicales, theirdevelopment of a bisporangiate strobilus with two setsof sporophylls, related to one another as they are in theflower of the Angiosperms, indicates a genetic relations
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