LINNEAN SOCIETY OF LONDOK. XXUl 



by Goetlie, and philosophically worked out by several of the most 

 eminent botanists. Upon this depends the whole system of phyllo- 

 taxy ; and many an important question of affinity must be decided 

 by a due discrimination of appendicular and directly axial organs or 

 parts. There are, however, cases where such a precise determina- 

 tion has proved difficult or impossible. The leaves of Piniis, the 

 outer casing of inferior ovaries, the floral cup of Myrtacece, some 

 parts of Coniferous flowers above alluded to, the stamens of 

 Euphorbia, &c. have led to much controversy as to whether they 

 are axial or appendicular. Amongst other arguments it has been 

 endeavoured to decide the question by tracing the development and 

 course of the vessels. It has been found, however, that the main 

 principles of growth and arrangement of the vessels are the same in 

 both, and that in fact no positive line of demarcation in this respect 

 can be drawn between an axial development and a true appendage. 

 It is consequently argued that there is no real difference between a 

 leaf-organ (or appendage) and a branch; and Trec\il (Comptes 

 Rendus, 1872, Ixxv. 655) goes so far as to propose the suppression 

 of the former term, and calling all the parts of a plant branches. 

 To ignore in Nature all classification where no positive limits can 

 be assigned, would be to abolish all method in its study. If we 

 treat all the parts of a plant as physiologically the same, and only 

 give them distinct names according to their functions, we put an 

 end to all study of homologies and affinities, excepting such as are 

 based on the very secondary adaptive characters. If a leaf or a 

 part of a leaf is capable of being occasionally converted into an 

 axis, if the end of an axis may occasionally develop iato a definite 

 leaf, if there are a few cases in which the exact point where the 

 sweUing of the axis terminates and the leaf-organ commences can- 

 not be fixed, if the differentiation of the axis and its appendages is in 

 many Cryptogams imperfect or null, these are not reasons sufficient 

 for ignoring the real almost constant and important differences 

 exhibited by the two classes in phaenogamous plants generally. 



At the same time, the demonstration of the susceptibility of rami- 

 fication of the leaf-organ, which we chiefly owe to French natu- 

 ralists, is a great point gained. If it takes place in a true vegetative 

 leaf, it results in its conversion into a true bud-bearing axis ; if in 

 the floral organs, they may still retain the determinate appendicular 

 character. In this way may, perhaps, be explained the production 

 of ovules on the margin or surface of carpeUary leaves, as suggested 

 by Casimir de CandoUe, the anomalous multiplication of stamens in 



