250 



THE FLOWER. 



which at best can well apply only to some special cases. The 

 word chorisis (x&purisi the act or state of separation or multiplica- 

 tion), also proposed by Dunal, does not involve any such assump- 

 tion, and is accordingly to be preferred. By regular multiplica- 

 tion, therefore, we mean the augmentation of the number of organs 

 through the development of additional circles; which does not 

 alter the symmetry of the flower. By chorisis we denote the pro- 

 duction of two or more organs in the place of one, through the mul- 

 tiplication of the leaf part of an individual phyton ; a case which 

 may be compared with the multiplication of cells by division (30), 

 and more directly with the division of the blade of a leaf into a 

 number of separate blades or leaflets. Chorisis may take place in 

 two different ways, which are perhaps to be differently explained : 

 in one case the increased parts stand side by side ; in the other, 

 they are situated one before the other. Both cases must evidently 

 disturb or disguise the normal symmetry of the flower. 



455. Of the first case, which may be termed collateral chorisis, 

 we have a good example in the tetradynamous 

 stamens (519) of the whole natural family Cru- 

 ciferae. Here, in a flower with symmetrical te- 

 tramerous calyx and corolla, we have six stamens ; 

 of which the two lateral or shorter ones are al- 

 ternate with the adjacent petals, as they normally 

 should be, while the four are in two pairs, one 

 pair before each remaining interval of the pet- 

 als ; as is shown in the annexed diagram (Fig. 

 292). That is, on the anterior and on the poste- 

 rior side of the flower we have two stamens 

 where there normally should be but a single one, 

 and where, indeed, there is but one in some spe- 

 cies of Crucifera3. Now it occasionally happens 

 that the doubling of this stamen is, as it were, ar- 

 rested before completion, so that in place of two 

 stamens we see a forked filament bearing a pair of 

 anthers ; as is usually the case in several species 

 of Streptanthus (Fig. 293). Here the two sta- 

 mens which* stand in the place of one may be compared with a 



/ 



FIG. 292. Diagram of a (tetradynamous) flower of the order Cruciferse. 

 FIG. 293. Flower of Streptanthus hyacinthoides, from Texas (the sepals and stamens re- 

 moved), showing a forked or double stamen in place of the anterior pair. 



