70 Morphology BOOK I 



made, but none withstood examination. The first idea 

 was that they might be regarded respectively as axial 

 and appendicular members, the leaf being an outgrowth 

 from the stem. But as branches of the stem must be 

 morphologically stems, and as they are appendages of 

 the stem, this distinction proves insufficient. The young 

 twig is axial as far as its relations to its leaves are con- 

 cerned, while it is appendicular as regards the stem of 

 which it is a branch. Again, a compound leaf has an 

 axis on which leaf-branches the leaflets arise, while it 

 is an appendage on a stem. A recognition of two classes 

 of appendicular organs, the branch arising in the axil of 

 the leaf, seemed to indicate a more fundamental difference, 

 that of relative position. This view received considerable 

 support, but there are so many exceptions to the arrange- 

 ment, that standing alone it, in its turn, is insufficient. 

 The outer leaves or scales of the leaf-bud, as well as the 

 leaves of the flower bear no branches in their axils. A third 

 attempt at a conception was more generally accepted 

 than either that the leaf is an outgrowth from an axis, 

 from which it differs in its organization and its structure. 

 This seemed, at first, more satisfactory, but it does not 

 seem decisive in the cases of the rachis of many compound 

 leaves, whose structure, at any rate, is fundamentally 

 similar to that of the stem which bears them. Moreover, 

 the organization of leaves and of winged stems is not 

 essentially dissimilar. If we apply the conception to 

 the Mosses we find the foliar expansions of the latter 

 comply with the conception, but no morphologist who 

 holds the antithetic theory admits that there is a true 

 homology between them (arising as they do on the 

 gametophyte), and the leaves of the higher plants, which 

 are all developed on the sporophyte. The sporangia of 

 Selaginella present another difficulty. They arise on the 

 stem, and they differ from it in organization but they 



