480 HISTORY OF PHYSIOLOGY. 



the tendencies and possibilities belonging to the 

 organization in which they occur. For instance, 

 the single wild-rose, by culture, transforms many of 

 its numerous stamens into petals, and thus acquires 

 the deeply folded flower of the double garden-rose. 

 We cannot doubt of the reality of this change, for 

 we often see stamens in which it is incomplete. In 

 other cases we find petals becoming leaves, and a 

 branch growing out of the center of the flower. 

 Some pear-trees, when in blossom, are remarkable 

 for their tendency to such monstrosities 3 . Again, 

 we find that flowers which are usually irregular, 

 occasionally become regular, and conversely. The 

 common snap-dragon (Linaria vulgaris) affords a 

 curious instance of this 4 . The usual form of this 

 plant is " personate," the corolla being divided into 

 two lobes, which differ in form, and together pre- 

 sent somewhat the appearance of an animal's face ; 

 and the upper portion of the corolla is prolonged 

 backwards into a tube-like " spur." No flower can 

 be more irregular ; but there is a singular variety 

 of this plant, termed Peloria, in which the corolla 

 is strictly symmetrical, consisting of a conical tube, 

 narrowed in front, elongated behind into five equal 

 spurs, and containing five stamens of equal length, 

 instead of the two unequal pairs of the didynamous 

 Linaria. These and the like appearances show that 

 there is in nature a capacity for, and tendency to, 



3 Lindley, Nat. Syst. p. 84. 



"* Henslow, Principles of Botany, p. 116. 



