380 THE NATURAL HISTORY REVIEW. 



of branches.* Of a similar nature were the leaves of Drosera^ 

 mentioned by M. Naudin.f 



Leaving this portion of the subject, we turn with much greater 

 satisfaction to other facts and reasonings brought forward by our 

 author to show that there is not so great a distinction between 

 foliar and axial organs as is usually supposed. Incidentally, it is 

 pointed out that the structure of the leaf-stalk is sometimes identical 

 with that of the stem, e.g. as in Richardia cethiopica. So in the 

 case of peltate leaves, it will be found that the structure of the 

 leaf-stalk is precisely similar to that of the young shoot, the ordi- 

 nary leaf-stalk, with its crescent-like arrangement of woody bundles, 

 and the groove upon its upper surface, seems to be so formed to 

 allow of room for the leaf-bud which lies in the furrow of the leaf- 

 stalk, and is thus protected from undue pressure ; but in the cylin- 

 drical leaf-stalks, the leaf-bud is secured from pressure by the 

 divergence of the leaf-stalk, or of the stem itself, or by other special 

 arrangements to which we need not now refer more at length. J And 

 as, in the above instances, the leaf-stalk has more or less of the 

 aspect of the stem, so may it also assume the aspect, and carry on 

 the functions of the leaves themselves, as in the so-called Phyllodes 

 in Acacias, OxaHds, etc. 



Other illustrations of a similar nature are offered by the Nepaul 

 Barley, the glumes of which bear florets on their midribs, and by 

 the stems of Cactacece^ and of many Euphorhiacea, which are pseudo- 

 foliar. But it must be remembered that in the two families just 

 mentioned, the resemblance to the leaf-type is more apparent than 

 real, the woody bundles retaining their cylindrical disposition even 

 in the most leaf-like portions of the stem, whereas in those cases 

 where genuine leaves are formed, as in FeresJcia, the fruit of some 

 species of Gereus, etc., the vascular bundles lose their cylindrical 

 disposition, are flattened out, and spread laterally, as in ordinary 



Other cases, such as Buscus, where the branch simulates a leaf, 

 are mentioned, and reference is made to the similarity in structure 

 between the midrib of a compound leaf and a branch. Indeed, in 

 some deeply divided leaves, e.g. Acanthus, a similar resemblance is 



• Ann. Sc. Nat. 3me Ser. xix. p. 241. 

 t Ann. Sc. Nat. 2me. Ser. xiv. p. 14. pi. i. f. 6. 



t On this point see also Darwin on Climbing Plants. Journ. Linn. See. vol. ix. 

 p. 113. 



