BOTANICAL SUBJECTS. 127 



serrations of these expansions, flower buds are developed. Why 

 the leaf -like expansions of the Fucus, the fern, the Phyllocactiis, 

 and Opuntia are not also called eladophyls I do not know. If it 

 be only a certain thinness of the branch leaf which gives it a claim 

 to be called " leaf," then the leaves of Cotyledon^ Crassula, and 

 others have no right to be called leaves. 



I would now ask " "What is the difference between the clado- 

 phyl of Xylophylla, with its flower-buds between its serrations, 

 and the rose-leaf, which has lost the power of producing flower- 

 buds between its serrations ? The difference cannot surely consist 

 in the one having parallel veins and the other reticulated veins. 

 For then all leaves of endogens would be eladophyls. 



The difference would appear to consist only in the one having 

 been called a cladophyl and the other a leaf I In other words, 

 one has been called a cladophyl because it retained the power of 

 producing buds between its serrations, and the other has been 

 called a leaf because it lost that power ! 



But as flower-buds and branch or leaf buds are interchano-eable,* 

 the leaf of Bryophyllum calycinum should logically be called a 

 cladophyl, for it has retained the power, though it does not always 

 exercise it, of producing buds between its leaf-crenations. 



The curious feature of all this is that the branches of Xylophylla 

 are deciduous, that is, they behave exactly like leaves, although they 

 have never been honoured with that name ! One cannot look at 

 the sub-di^-isions of a fern frond, say of Woodwardia, the sub- 

 divisions of the stem of a Xylophylla, the sub-divisions of the 

 stem of an Australian acacia, and those of a seaweed, without 

 considering them all as one and the same thing, although they 

 have been severally distinguished by the names of frond, cladophyl, 

 and phyllodium. 



* The interchangeability of floAver and leaf buds is well known to 

 horticulturists. If at a certain stage of a fruit tree, when the buds are neither 

 flowers nor leaves, but embryos of both, manure and elements of luxuriant 

 growth are given, they run the risk of getting plenty of leaves, and very 

 little fruit. The tree very often does this of its own accord every second 

 year. This shows that the same bud will produce leaves or flowers according 

 to circumstances. Therefore, the cells which produce leaves must be 

 essentially the same which produce sepals, petals, stamens, carpels, and 

 ovules ! That is the vegetative cells are identical with the reproductive 

 cells. 



