TERATOLOGY — SUPPEESSION OF OEGANS. 367 



instances the parts wMch are afterwards suppressed can be seen in the 



early stages of growth, and occasionally some vestiges of them remain 



in the fuUy developed flower. Sometimes 



the whorl of the petals is wanting, the 



flowers being apetalous (a, privative, and 



■riraXov, a leaf) (fig. 642), and in such cases 



it is common to see the stamens opposite to 



the segments of the calyx which is the whorl 



^verticil) next to them, as in Chenopodiacere ^^- **^- ^'s. 64S. 



(fig. 643). That this suppression of the petals takes place is shown 



in the case of certain allied plants, as in the natural orders Caryophyl- 



lacese and Paronychiacese, where some species have petals and others 



want them. 



By the suppression of the verticil of the stamens, or of the carpels, 

 flowers become unisexual (unus, one, and sexus, sex), or diclinous (big, 

 twice, and xXhn), a bed, and are marked thus, S 9 ; the first of these 

 symbols indicating the male, and the second the female flower. Thus, 

 in Jatropha Curcas (fig. 346, p. 218), the flowers have five segments 

 of the calyx, and five petals, while in some (fig. 346, 1) the pistil is 

 wanting ; in others (fig. 346, 2), the stamens. In the genus Lychnis 

 there are usually stamens and pistU present, or the flower is hermaphro- 

 dite, or monoclinous (/j^ovo;, one, and xXhrj, a bed) ; but in Lychnis 

 dioica some flowers have stamens only ; others pistils only. Thus it 

 is that monoecious or monoicous and dioscious or dioicous [imovos, one, big, 

 twice, and ohiov, a habitation) plants are produced by the suppression 

 of the essential organs of the flowers, either in the same or in different 

 individuals of the same species ; while polygamous [irdk-jg, many, and 

 yai/iog, marriage) plants are those in which, besides unisexual, there 

 are also hermaphrodite or perfect flowers. 



Some parts of the pistil are generally suppressed in the progress of 

 growth, and hence it is rare to find it symmetrical with the other 

 whorls. When the fruit was treated of (p. 299) it was shown that 

 carpels and ovules often become abortive by pressure and absorption, 

 so that the pericarp and seeds differ in their divisions and numbers 

 from the ovary and ovules. If the whorls of the calyx and coroUa are 

 wanting the flower becomes naked or achlcmiydeous (p. 177). It may 

 still, however, be fitted for the functions of producing seed ; but if 

 the essential organs — viz. the verticils of stamens and pistils — are sup- 

 pressed, then the flower, however showy as regards its envelopes, is 



Fig. 642. Diagram of the flower of Glaux maritima, showing the suppression of the verticil 

 of the corolla. There are five divisions of the calyx, Ave stamens alternating with them, 

 and five divisions of the ovary, with a central plaoentation. Fig. 643. Diagram of the 

 flower of Chenopodium album, showing the suppression of the verticil of the corolla. The 

 five stamens, in this case, are opposite to the divisions of the calyx, thus exhibiting the 

 arrangement which might be expected from a non-development of the corolla. The divisions 

 of the ovaiy are not easily seen, the placentation being central. 



