252 Dr. A. Arber. On the Development and 



I find that in all these species — Fan- and Feather-palms alike — the 

 mechanism of development of the plicated or lamellated limb follows 

 essentially the same lines. For the sake of brevity, I will limit myself 

 to three cases as examples. In the Fan-palm, Trachycarpus Fortunei 

 (fig. 1, A-F), the second plumular leaf, examined at a very young stage, 



ABC D E F 



Fig. 1. — Trachycarpus Fortunei, H. Wendl. Series of transverse sections from below 

 upwards through the second plumular leaf of seedling ( x 23). (Sections cut by 

 Miss Ethel Sargant.) Fig. 1, A, sheath ; fig. 1, B, petiole ; fig. 1, C-E, process 

 of invagination ; fig. 1, F, final form. In fig. 1, E, the grooves are numbered in 

 the order of their appearance. [Throughout figures — xylem represented black ; 

 phloem, white ; fibres, dotted.] In this figure only principal bundles included. 



was found to have at the base a closed sheathing region (rig. 1, A) ; this 

 was succeeded by the petiole (fig. 1, B), an organ of roughly triangular 

 outline with a concave upper surface. The petiole retained this char- 

 acteristic form for a very short distance only (about 20/x,), and then the 

 lamellate structure was rapidly reached by the development of a series 

 of grooves penetrating deeply into the leaf-stalk tissue between the 

 vascular bundles (fig. 1, C-F). In fig. 1, E, I have numbered the grooves 

 to show the order of their origin. The process, of grooving is a very rapid 

 one, the stages between fig. 1, B, and fig. 1, E, taking place within a distance 

 of about 05 mm. 



a b c D E 



Fig. 2. — Cocos Romanzoffiana, Cham. Series of transverse sections from below *i 

 upwards through second foliage leaf of seedling (xl4). Fig. 2, A, sheath; 

 fig. 2, B, petiole ; fig. 2, C-E, stages in invagination. 



That development proceeds on the same general principle in both Feather- 

 and Fan-palms, is demonstrated by the comparison of fig. 1, A-F, with 

 fig. 2, A-E, drawn from the second foliage leaf of Cocos Romanzoffiana. This 



