THE MORPHOLOGICAL COMPOSITION OF PLANTS. 49 



an ordinary stem-structure. One further fact is to 



be noted. At the same time that their leaf-like appearances 

 are lost, the axes also lose 

 their separate individuali 

 ties. As they become stem- 

 like, they also become inte 

 grated; and they do this so 

 effectually that their origi 

 nal points of junction, at 

 first so strongly marked, are effaced, and a consolidated trunk 

 is produced. 



Joined with the facts previously specified, these facts 

 help us to conceive how, in the evolution of flowering plants 

 in general, the morphological components that were once 

 distinct, may become extremely disguised. We may ration 

 ally expect that during so long a course of modification, 

 much greater changes of form, and much more decided fusions 

 of parts, have taken place. Seeing how, in an individual 

 plant, the single leaves pass into compound leaves, by the 

 development of their veins into mid-ribs while their petioles 

 begin to simulate axes; and seeing that leaves ordinarily 

 exhibiting definitely-limited developments, occasionally pro 

 duce other leaves from their edges ; we are led to suspect the 

 possibility of still greater changes in foliar organs. When, 

 further, we find that within the limits of one natural order, 

 petioles usurp the functions and appearances of leaves, at the 

 same time that in other orders, as in Ruscus, lateral axes so 

 simulate leaves that their axial nature would by most not be 

 suspected, did they not bear .flowers on their mid-ribs or 

 edges; and when, among Cactuses, we perceive that such 

 metamorphoses and re-metamorphoses take place with great 

 facility; our suspicion that the morphological elements of 

 Phsenogams admit of profound transformations, is deepened. 

 And then, on discovering how frequent are the monstrosities 

 which do not seem satisfactorily explicable without admitting 

 the development of foliar organs into axial organs ; we become 

 50 



