MOKPHOLOGY OF EEPRODUCTIVE ORGANS 137 



eaoli carpel has at its base on the outside a little greenish scale, 

 a, a, which is supposed by some to be due to it. 



It will be observed that, in the above cases of transverse 

 chorisis, the parts which are produced do not resemble those 

 from which they arise, and this appears to be a universal law in 

 this form of chorisis. 



Collateral Chorisis. — We have a good example of this form 

 in the Stock, Wallflower, and other plants of the order Cruci- 

 ferse (fig. 252). Within the perianth we find six stamens ; of 

 these two are placed opposite to the lateral sepals, while the 

 other four are placed in pairs opposite the anterior and posterior 

 sepals ; we have here, therefore, four stamens instead of two, 

 which result from the collateral chorisis of those two. In some 



Fig. 252. 



Fig. 253. 



Fig. 254. 



Fif/. 253. Biagi-am of the flower of the commou Wallflower. /■'/-/. ■2bi<. 



Plower of a species of Streptanthus, with tbe floral envelopes removed, 

 slioAviug a forked stamen in place of the two anterior stamens. From 

 Gray. Fig. 254. Diagram of the flower of the Fumitory. 



Cruciferse, as Streptanthus (fig. "233), we have a strong confir- 

 mation of this view jpresented to us in the fact that, in place of 

 the two stamens, as commonly observed, we have a single fila- 

 ment forked at the top, and each division bearing an anther, 

 which would seem to arise from the process of chorisis being 

 incompletely carried out. The flowers of the Fumitory are also 

 generally considered to afford another example of collateral 

 chorisis. In these we have two sepals (fig. 254), four petals in 

 two rows, and six stamens, grouped together into two bundles 

 or phalanges. The central one of each bundle bears a two-lobed 

 anther, the lateral ones have only half an anther each. This 

 has been held to arise from chorisis of two original stamens. It 

 is possible, however, to regard each phalanx or bundle of stamens 



