. The classification of flowering plants. Plants. 144 FLOWERING PLANTS [CH. Where bracteoles are absent, they may sometimes be re- garded as merely suppressed as in the Cruciferae, where the arrangement of the dimerous calyx is that of a bracteolate flower, the outer pair of sepals being antero-. posterior (fig. 59). Where, however, the bracteoles are to be regarded as typically absent, the two first developed floral leaves generally occupy as near as may be the position of the absent prophylls. Thus the dimerous calyx of Francoa is transverse, and the two outermost sepals of Primulaceae are F
. The classification of flowering plants. Plants. 144 FLOWERING PLANTS [CH. Where bracteoles are absent, they may sometimes be re- garded as merely suppressed as in the Cruciferae, where the arrangement of the dimerous calyx is that of a bracteolate flower, the outer pair of sepals being antero-. posterior (fig. 59). Where, however, the bracteoles are to be regarded as typically absent, the two first developed floral leaves generally occupy as near as may be the position of the absent prophylls. Thus the dimerous calyx of Francoa is transverse, and the two outermost sepals of Primulaceae are Fig. 67. Floral lateral (fig. 58). diagram of Vicia ° i -t , . Faba. From Willis. in many cases subsidiary bracteoles in- tervene between the ordinary single one or pair and the flower; the arrangement of the flower is then influenced by their number and position (see Juncaceae). The calyx, though generally green and leaf-like, serving to protect the more delicate floral leaves, is sometimes white or coloured and resembles a corolla. Such petaloid calyces are frequent where the corolla is absent or small and inconspicuous, as in several genera of Ranunculaceae. The individual sepals may be free, that is, inserted separately on the receptacle (calyx polysepalous), or be more or less completely united (calyx gamosepalous). In the latter case we can generally distinguish a lower tube crowned by lobes or segments, or teeth, the number of which indicates the number of sepals present. Occasionally sepals are stipulate; the cohesion of the stipules of adjoining sepals gives rise to the epicalyx ( Potentilla, fig. 62). As regards duration, the calyx may disappear when the flower opens (caducous, as in the Poppy order), or remain till pollination occurs, or during the life of the flower (deciduous), or last after the flower passes into the fruit (persistent, as in the Rose order). In the last case it may aid in the distribution of the fruit. As in the case of the corolla, the indivi
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