22 Traces of Unity in Plants. 



but, as often happens, this very difference is a proof of 

 unity. In point of fact, every leaf has a similar endow- 

 ment. What, it may be asked, are the processes which 

 cause the edges of a simple leaf to be serrated in various 

 ways, and what is the significance of the leaflets of the 

 composite organ ? No other interpretation can be offered 

 than this that the processes are the rudiments of the 

 leaflets that many leaves are present potentially in every 

 single leaf. Buds are constant elements in the leaves of 

 the Bryophyllum calycinum and Malaxis paludosa ; and 

 not unfrequently they may be developed in the leaf of 

 the orange after it has fallen from the tree. Ovules and 

 sporules may also be singled out as indicating a bud- 

 producing faculty in the carpel and frond respectively, 

 both of which organs are only leaves in other forms. 

 And, therefore, the buds of the quasi-leaf of the Phyllo- 

 cactus, instead of being evidences of singularity, are 

 evidences of similarity, which make the organ more leaf- 

 like rather than less leaf-like. By the alteration and 

 coalescence of these leaf-elements, the branches and 

 stem of the Phyllocactus are evidently built up ; and 

 what happens here is the rule everywhere. All branches 

 and stems are composed of bud-producing nodes, which 

 are substantially bud-producing leaves. In the succulent 

 euphorbiaceae, for example, traces of rudimentary buds 

 are as common as in the cactaceae. In the Chamaerops 

 and bamboo, the joints of the stem present numerous 

 minute processes, the germ-like nature of which is 

 shown by the sprouts which often form in these places 

 when the plant happens to lie flat on the damp ground. 

 On the pseudo-bulbs of the orchids, also, traces of similar 

 processes are to be found which often behave in the 

 same manner : and in every stem, though the fact may 

 not be so apparent as in the instances which have been 



