. The classification of flowering plants. Plants. 140 FLOWERING PLANTS [CH. flower with a polycyclic androecium and gynoecium (see also Alismaceae). An increase in the number of whorls beyond what is for any reason regarded as typical is termed pleiotaxy. Thus compared with the monocotyle- donous type as represented by Liliaceae, the polycyclic gynoecium of Alisma or Butomus are instances of pleiotaxy. If on the other hand these were taken as the standard of comparison, the trimerous gynoecium of Liliaceae would shew a decrease in the number of whorls, or oligotaxy. Keeping however to the one
. The classification of flowering plants. Plants. 140 FLOWERING PLANTS [CH. flower with a polycyclic androecium and gynoecium (see also Alismaceae). An increase in the number of whorls beyond what is for any reason regarded as typical is termed pleiotaxy. Thus compared with the monocotyle- donous type as represented by Liliaceae, the polycyclic gynoecium of Alisma or Butomus are instances of pleiotaxy. If on the other hand these were taken as the standard of comparison, the trimerous gynoecium of Liliaceae would shew a decrease in the number of whorls, or oligotaxy. Keeping however to the one standard as represented by Liliaceae, oligotaxy finds an illustration in the absence of a whorl of stamens in the Iridaceae. It must be borne in mind that these terms are only relative, and depend entirely on the standard selected, which may be quite an arbitrary one. From an evolutionary point of view it may be more cori-ect to regard the ordinary monocotyledonous " type" as derived by oligotaxy from a flower with polycyclic whorls. A similar comparison may be made between the two genera of Caryo- phyllaceae, floral diagrams of which are given in fig. 63. A common instance of pleiotaxy is the doubling of flowers where the corolla becomes Fig. 63. Floral diagrams of A Sileiie injiata and B Paronychia sp. shewing the ordinary type of flower in the tribe Silenoideae and the most reduced type of the tribe Alsinoideae ; a, /3, bracteoles. After Eichler. An arrangement of the androecium which occurs in several orders of Dicotyledons calls for remark. Two whorls of stamens are present, but this diplostemony is complicated by the fact that the members of the outer whorl are opposite the petals. 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 Rendle, A. B. (Alfred Barton), 1865-1938. Cambridge
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