862 



ORGANOGRAPIIV. 



Transverse chorisis is also frequently to be found in the stamina! 

 Avhorl, but it is less frequent in the gynoecium. Examples of 

 chorisis in the carpels are furnished, however, bv Seduni (Jig. 

 566), and Crassula {fig. 763), where each carpel has at the base 

 on its outside a little greenish scale, which is supposed by some 

 to be due to it. 



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

 chorisis, the parts which are produced do not resemble those 

 from which they arose, and this appears to be an universal law 

 in tliis form of chorisis. We now pass to 



Collateral chorisis. — We have a good example of this form in 

 the Stock, Wallflower, and other plants of the Jiatural order 

 Cruci ferae. In tliese flowers, the two floral envelopes are each 

 composed of four orgmns alternating with each other (fig. 772). 

 Within these we find six stamens instead of four, as should be 

 the case in a symmetrical flower; of which two are placed oppo- 

 site to the lateral sepals and alternate with the adjacent petals, 

 while the other four arc placed in pairs opposite the anterior and 

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

 two, which results from the collateral chorisis of those two. In 

 some Crucifera, as Streptanthus (fig. 773), we have a strong 

 confirmation of this view presented to us in the fact that, in place 



Fig. 773, 



Fig. 772 



Fig. 774. 



Ftg. 112. Diagram of the flower of the common Wallflower Fig. 773. Flower 



of a species of .Stri])tnnthus, with the floral envelopes removed, showing a forked 



stamen in place of the two anterior Btamens. From Gray Fig. 774. Diagram 



of tiie flower of Funiitor>, 



of the two stamens, as thus commonly observed, we have a 

 single filament forked at the top, and each division bearing an 

 anther, which would seem to arise from the jirocess of chorisis 

 being arrested in its progress. Tiie flowers of the Fumitory are 

 also generally considered to aflord another exami)le of collateral 

 chorisis. In the flowers of this jdant we have two sepals (fig. 

 774), four petals in two rows, and six stamens, two of which 



