Morphology of the Leaves of Palms. 



255 



product, since it does not penetrate into the grooves. Deinega and Hirmer, 

 who applied microtome technique to the problem of the origin of this 

 membrane, conclude that it arises through secondary fusions occurring at the 

 angles of the folds of the plicate leaf. My observations are entirely in 

 harmony with this view, which was also indicated many years ago by Eichler. 

 In some serial sections of the plumular leaves of Trachycarpus Fortunei and 

 Thrinax excelsa, cut by Miss Ethel Sarganfc, I have been able to observe 

 proliferated epidermal cells occluding the mouths of the invaginations 

 (fig. 4, A-C). This occluding tissue no doubt represents the delicate early 



A D 



Fig. 4. — Epidermal proliferations in seedling leaves, from sections cut by Miss Ethel 

 Sargant. Fig. 4, A-C, Thrinax excelsa, Lodd. Fig. 4, A, transverse section of 

 third plumular leaf ( x 47) ; m.b., median bundle. Fig. 4, B, mouth of invagina- 

 tion marked x in fig. 4, A ( x 318). The epidermis and its proliferation, which 

 occludes the opening of the groove, are dotted. Fig, 4, C, another occluded 

 groove, from lower down in the same leaf ( x 318). Fig. 4, D, Chamcerops 

 Fortunei, Wendl. Mouth of invagination occluded by epidermal outgrowth, 

 from a transverse section similar to that shown in fig. 1, F ( x 318). 



stage of the membrane which, later on, becomes so conspicuous a feature of 

 the young leaf. The condition observed in these two genera thus confirms 

 Hirmer's view, which was based on a study of another genus — Phcenix. It is 

 much to be desired that some botanist, working at a tropical station where 

 the leaves of a number of growing Palms are available, would give us a 

 comprehensive account of the structure and history of the " coiffe." 



3. The Terminal " Gland." 



Attention was drawn by Baillon* in 1895 to the fact that the first leaves 

 produced by a Palm seedling are usually entire and parallel-nerved, and end 

 in " une sorte de glande terminale, appareil excreteur, dont l'existence est 

 passagere." I have observed this apical structure in the plumular leaves 

 of Phcenix dactylifera (fig. 5, A-C) and Pritchardia filifera (fig. 5, D-F). In 

 these cases the main-part of the leaf-limb is, as usual, dorsiventral, whereas the 



* Baillon, H. (1895). 



