CHOKISIS OR DEDUPLICATION. 



243 



454. Choiisis or Dcduplication, The name dedouhlement of Dunal, 

 which has been translated deduplication, literally means unlining ; 

 the original hypothesis being, that the organs in question unline, or 

 tend to separate into two or more layers, each having the same 

 structure. We may employ the word deduplication, in the sense 

 of the doubling or multiplication of the number of parts, without 

 adopting tins hypothesis as to the nature of the process, which at 

 best can well apply only to some special cases. The word chorisis 

 .(xa>p""f, the act or state of separation or multiplication), also pro- 

 posed by Dunal, does not involve any such assumption, and is ac- 

 cordingly to be preferred. By regular multiplication, therefore, we 

 mean the augmentation of the number of organs through the de- 

 velopment of additional circles ; which does not alter the symmetry 

 of the flower. By chorisis we denote the production of two or more 

 organs in the place of one, in a mai?ner analogous to the division of 

 the blade of a leaf into a number of separate blades, or leaflets. 



455. Chorisis, or the division of an oi'gan into a 

 pair or a cluster, may take place in two ways. 

 In one case the parts or organs thus produced 

 stand one before the other ; in the other case they 

 stand side by side. The first is named transverse 

 chorisis ; the second, collateral chorisis. Both 

 must evidently disturb or disguise the normal 

 symmetry of the blossom. 



456. Collateral Chorisis is that in respect to 

 which there is least doubt as to the nature of the 

 process. We have a good example of it in the 

 tetradynamous stamens (519) of the Mustard or 

 Cress family (Fig. 406). Here, in a flower with 

 a symmetrical tetramerous calyx and corolla, we 

 have six stamens ; of which the two lateral or 

 shorter ones are alternate with the adjacent 

 l^etals, as they normally should be, while the four 

 are in two pairs, one pair before each remaining interval of the 

 petals ; as is shown in the annexed diagram (Fig. 367). That is, 

 on the anterior and on the posterior side of the flower we have two 

 stamens where there normally should be but a single one, and where, 



riG. 367. Diagram of a (tetradynamous) flower of the order Cruciferse. 

 FIG. 368. Flower of Streptanthus byacinthoides, from Texas (the sepals and stamens re- 

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



