CHORISIS OR DEDUPLICATION. 



243 



454. Chorisls or Dednplieation. Tlie name dedoublement of Dunal, 

 which lias been translated dednplieation, 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 dednplieation, in the sense 

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

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

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

 (xcoptcrir, 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 manner analogous to the division of 

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



455. Chorisis, or the di\-ision of an organ 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 

 n^ust evidently disturb or disguise the normal 

 spnmetry 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 



tetradrjnamous 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 



petals, as they normally should be, while the four 



ai'e 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, 



363 



PIG. 367. Diagram of a (tetradynamous) flower of the order Crucifene. 

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

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



