230 



ORGANOGRAPHY. 



apetaloid. The corolla is usually the most showy and conspicu- 

 ous part of the blossom, and what in common language is termed 

 the flower. In some rare cases, however, it is green like the 

 calyx, as in certain Coboeas and Asclepiadaceous plants. The 

 corolla is also, in the majority of flowers which possess odoriferous 

 properties, the seat of those odours. Sometimes, as we have seen, 

 there is a gradual transition from the sepals to the petals, as in 

 the White Water-Lily (NymphcEa) (Jig. 438) ; in the same plant 

 there is also a similar transition from the petals to the stamens. 

 In structure the petals resemble sepals and leaves, being com- 

 posed of parenchyma, supported by veins which are chiefly 

 formed of true spiral vessels. These veins are generally re- 

 ticulated. The whole petal is invested by a layer of epidermis, 

 which is usually destitute of stomata, but these organs may be 

 sometimes found on the lower surface. The corolla is generally 

 smooth, although hairs occasionally occur, as in the Bombax ; 

 when they exist they are usually coloured, as in the Buck- 

 bean, and on the inner whorl of the perianth of the Iris, which 

 corresponds in position to the corolla. Petals are frequently 

 naiTOwed below into a stalk-like portion, which is analo- 

 gous to the petiole of a leaf, as in the Wallflower {Che'a-an- 



thus) {fig. 421, p) 

 Fig. 460. Fig. 461. and Pinks {Dian- 



thus) (Jigs.460si,m\ 

 461) ; the narrow- 

 ed portion is then 

 termed the unguis 

 or claw {fig. 461, 

 o), the expanded 

 portion the limb 

 {fig. 461, /), and 

 the petal is said to 

 be wigniculate or 

 clawed. In this par- 

 ticular petals must 

 be considered to re- 

 semble leaves more 

 than the sejjals do, 

 as the latter organs 

 arc almost without 

 exception sessile, or 

 without claws. 



The outline of 

 petals, like those of 

 leaves, is subject to great variation. Thus, they may be linear, 

 oblong, lanceolate, elliptic, orbicular, ovate, cordate, &c. The ap- 

 plication of these terms having been already fully explained when 

 speaking of leaves, need not be further alluded to. The condition 



Fi(j. 460. The flower of a species of Pink (Dianlhus). 



b. Bracts, c. Calyx, p. Petals, e. Stamens. 



Fig. 4<!1. One of the petals of the same flower, o. 

 Claw or unguis. I. Limb, wliich is fringed ut the 

 margin. 



