48 THE STRUCTURE OF FLOWERS. 



CHAPTER V. 



THE PRINCIPLE OF COHESION. 



Cohesion. — General Observations. This term signifies the 

 ■union between parts of the same kind or whorl ; and the 

 prefix gamo- is used in conjunction with the terminations 

 -sepalons, -petalons, and -phyllous, — to indicate that the parts 

 of the calyx, corolla, and perianth respectively cohere. In 

 the case of the stamens, they are said to be mon-, di-, tri-, or 

 poly-adelphous, according as the filaments cohere into one, 

 two, three, or more groups ; while syngenesious is used for 

 the coherence of anthers, and, lastly, syncarpous denotes that 

 the carpels of a pistil cohere. 



There are two kinds of cohesion, congenital and by con- 

 tact.* Congenital cohesion I regard as an advance upon 

 freedom, or a further state of differentiation ; for, according 

 to the principles of Evolution, freedom or separation of parts 

 must precede their union ; jnst as, for example, bones are 

 free in the embryo which beconle " ankylosed " in the adult ; 

 or always free in a fish, while their homologues cohere in 

 higher types of vertebrates. 



Congenital cohesion applies to by far the greater number 

 of cases of union amongst the parts of the different whorls 



* We might appropriately distinguish these two kinds of union by 

 the terms connate or "born together," and coherent or "sticking 

 together." 



