62 THE STRUCTURE OF FLOWERS. 



CHAPTER VII. 



THE PEiNCiPLE OP COHESION — Continued. 



Cohesion of Cakpels, or Syncakpous Pistil. — The accepted 

 doctrine tliat the carpels are metamorphosed leaves, will be 

 considered more fully when teratological modifications 

 come to be discussed ; and the proof that an ordinal^ 

 carpel, such as a legume, is merely a leaf folded upon itself 

 in a condnplicate manner with the margins coalescing and 

 then metamorphosed into a new organ, requires no special 

 evidence now. That a syncarpous pistil consists of two or 

 more carpellary leaves coalescing is equally admitted; and 

 there are two methods of cohesion. Either the carpels may 

 be ah initio composed of unclosed leaves, which cohere by their 

 edges * respectively in contact, thus forming a single cavity 

 provided with parietal placentas, — such a union implying 

 a more primitive or arrested condition, from an evolutionaiy 

 point of view ; f or they may be individually more or less 

 closed before coalescence takes place, in this case by their 

 lateral surfaces. The axile placentation is the result. The 



• The theory that the placentas are, at least in part, azial, will be 

 seen to be erroneona in conseqnence of the orientation of their rascnlar 

 cords (e.g. Pig. 12, c, p. 64; and Fig. 13, a, h, p. 65). 



f Thns the parietal placentation of Orobanche ia probably a result 

 of degradation through parasitism, from the azile, of the Scrophuiarinea. 

 It may be compared to a " cleft palate " and " hare-lip " in man. 



