PHANEROGAMIA I FOLIAR ORGANS. 267 



and the axis, in consequence of which the leaf is, after a certain time, 

 thrown off from the axis, while in other cases it gradually dies and 

 decays on the axis itself. This true articulation is often repeated 

 in the continuity of one and the same leaf, either only so that a 

 joint is formed between the petiole and the lamina (e. g. in Citrus, 

 DioncBa), or in such a manner that in the flat sub-divided leaves 

 (e. g. f. pinnatisecta, palmatisecta, &c.), every lobe is connected to 

 the main body by a joint. These latter are called compound leaves 

 (y*. composita), and, according to the subdivision, digitate or 

 pinnate (f. digitata, pinnata, &c.). The separate parts are named 

 leaflets {foliola), and the part connecting all these is the common 

 petiole (petiolus communis). The leaflets can of course assume all 

 the forms of the leaf, in particular they may be again separated into 

 lamina, petiole, and pulvinus. In some New Holland Acacias 

 (e. g. Ac. heterophylla) the first leaves are compound ; they gradually 

 form fewer and fewer leaflets, till at last the part corresponding to 

 the common petiole alone remains, which then appears as a perpen- 

 dicular plate, and is called a pliyllodium, to distinguish it from the 

 other perfect leaves of the same plant. 



Botanists who imagine that the object of Botany is merely the correct 

 definition of many species for their herbaria, will blame me for super- 

 ficiality and want of profundity, in that I have so briefly and roughly 

 treated the forms of leaves, which are the most essential grounds for the 

 definition of species. I cannot help this : I merely find in these, as it 

 ]imy happen, good and bad methods of nomenclature for various partly 

 or wholly divided surfaces or borders, for filiform or solid forms, nothing 

 at all botanical, much less, therefore, the properly scientific part of 

 botany. If a slender filiform leaf be called a petiole, I have no objec- 

 tion to it, if nothing else be called by this name but a stalk-like leaf; but 

 when it is superadded that the lamina is suppressed here, this is unscien- 

 tific and false : if a leaf merely developed into a plate be alone called 

 folium sessile, there is nothing to be said against the term ; but when, in 

 addition, it is said that the petiole is abortive here, this is again pure 

 imagination. Whence in all the world does it follow from the essence of 

 a plant that a leaf must regularly consist of lamina and petiole ? The 

 entire method in use up to this time, of describing the leaf according to 

 blade and stalk, and of reducing all other forms under this conception, 

 might so far have value, if we would, from the analogy of zoology, hold 

 by the most perfect form, in order to obtain a type, with which to connect 

 all others as deviations ; then, however, we must start from the com- 

 pound leaf, as evidently the most perfect. But it is as false to call all 

 deviations, abortions, and Nature's unsuccessful attempts at forma- 

 tion, as it would be ridiculous to say that in Monas lens the toes and 

 nails, the cartilage of the ear, &c. were abortive. Expressions such as 

 " Nature has here attempted, she has here deviated from her type," are 

 altogether unscientific, and no better than childish anthropopathy. In 

 Mesembryanthemum^ for instance, Nature has not deviated frotri the type 

 of leaf-formation, but her type is different here from what it is in other 

 plants ; each in its kind is perfect, attaining the grand purpose of all ve- 

 getable development, the development of the most manifold construction 

 of form from the very simplest elements. 



