THE CALYX. 



131 



stand opposite those of the one exterior to it, a vertical 

 line may be placed between the symbols, thus : C 5 | A 6 . 



202. Other methods of indicating symbolically the 

 relations of the parts of the flower are in vogue ; the one 

 just given is recommended by Prantl, and is sufficiently 

 convenient. 



203. It has already been mentioned that flowers are 

 said to be irregular when the members of any whorl are 

 of different sizes or shapes, as, for example, in the Pea ; 

 and regular, when the opposite is true. Fig. 173 repre- 

 sents one of these regular flowers. A moment's reflection 

 will show that any line whatever drawn across the centre 

 of this diagram will divide it into two exactly similar 

 halves. The term actinomorpMc, as well as " regular," is 

 applied to all such flowers. Flowers, on the other hand, 

 which can be cut symmetrically in one vertical plane only 

 are zygomorphic. 



204. In this book, as in most English books, the term 

 " symmetrical " is employed to indicate that the whorls 

 consist of the same number of members each, and it is, in 

 fact, the same in meaning as "isomerous." The later 

 German botanists define a symmetrical flower as "one 

 which can be divided vertically into two halves resembling 

 each other like an object and its reflected image." 



We shall now proceed to consider in detail the variations 

 in form assumed by the floral organs individually. 



205. The Calyx. As you are now well aware, this 

 term is applied to the outer circle of floral leaves. These 

 are usually green, but not necessarily so ; in some Exogens, 

 and in nearly all Endogens, they are of some other colour. 

 Each division of a calyx is called a sepal, and if the sepals 



