214 



ORGANOGRAPHY. 



here -we have two sepals inferior, two lateral, and one superior ; 

 while in the corolla there are two petals superior, two lateral, 

 and one inferior {fig. 460). 



The same definite relation with respect to the axis also holds 

 good in many cases in the staminal and carpellary whorls, by 

 which important distinctive characters are frequently obtained, 

 as will be seen afterwards when treating of Systematic Botany. 



Section 3. The Floral Envelopes. 



1. THE CALYX. 



"We have already stated that the calyx is the outermost 

 envelope of the flower, and that it is composed of one or more 

 leafy organs called sepals. These sepals are xisually green like 

 true leaves, by which character, as well as by their position 

 and more delicate texture, they may in most cases be distin- 

 guished from the petals. There are numerous instances, how- 

 ever, in which there is a gradual transition from the sepals to the 

 petals, (especially when there is more than one whorl of these 

 organs,) so that it is difficult or almost impossible to say where 

 the calyx ends and the corolla begins. The "White "Water Lily 

 \Nympk(sa alba) {fig. 436), affords a familiar and good illustra- 



Fig. 436. 



Fig. 436. Flower of the White Water-Lily (Nymphcea alba) reduced in 

 size. After Jussieu. c, c, c, c. The four sepals, p, p, p, p. Petals, e. 

 Siamens. The parts ou the right show the gradual transition from 

 the calyx c to the petals p, and from these organs to the stamens e. 

 The stamens from 1 to 5 are gradually more distinctive. 



tion of this. In some plants again, the green colour disappears, 

 and the calyx becomes coloured with the same tints as the corolla, 

 or with some other hues. In such cases it is said to be petaloid, 

 and the chief distinctive character between it and the corolla is 



