ORGAKS OF REPRODUCTION. 



35: 



petals, eight or ten stamens, and a four or five-lobed pistil; in 

 the Iris, there are three organs in each whorL All the above 



Fig. 763. 



Fig. 764. 



^^^^ 



Fiff.TGS. T\oweT of Craxsula rubens. c,c. Sepals. ;),/>. Petals 

 o, o. Carpels, at the base ot each of whicli is seen a scale, 

 Flower oi' Scdurn. 



e.e, e. Stamens. 

 I, a Fig. 764. 



are therefore symmetrical flowers. "When the number of parts in 

 each whorl docs not correspond, or when the parts of a Avhorl 

 are not multiples of one another, the flower is unsymmetrical, as 

 in Verbena {fig. 391), Avhere the calyx and corolla have five 

 parts in each whorl, and the stamens and pistil only four. 



A symmetrical flower, in which the number of parts in each 

 whorl is the same, as in Crassula {fig 763), is said to be 

 isomerous ; or when the number is unequal, as in Rue {figs: 564 

 and 596), and Sedum {fig. 764), the flower is anisomeruus. 

 The number of parts is indicated by a Greek numeral prefixed 

 to the word meros, signifying a part. Thus when there are two 

 parts in tlie whorls, as in Circcea {fig. 765), the flower is 

 dimerous, 2i\\{\. the symmetry is said to be 

 binary or tivo-membered : this may be con- 

 sidered as answering to the distichous or 

 two-ranked aiTangement of leaves {fig. 

 267); each whorl forming one cycle com- 

 posed of two parts the internodes between 

 the several parts not being developed, or 

 to successive pairs of opposite leaves de- 

 cussating with each other. This aiTange- 

 ment is thus marked ^/. When there are ^'^: ''f'^- 

 tliree parts in a whorl, as in the Squill 

 {fiy. 424), Iris, and Lily, the flower is trimerous, and the 

 symmetry is ternary, trigonal, or triangular; it is indicated 

 thus, ^. This may be regarded, either as answering to the 

 tristichous arrangement of leaves, each whorl forming a cycle 

 of three organs, the internodes between them not being de- 

 veloped; or to successive whorls of three organs in each. When 

 there are four parts in a whorl, as in Rue {fig. 564), the flower 



A A 3 



Diagram of 

 the flower of Circcea. 



