116 Bulletin Jard. Bot. Buitenzorg, Série 111, Vol. V. Livr. 2. 



penetrate in a defiiiite relation with respect to the preceding or succeeding 

 one, the side of the cône directly above it. One can also liken a developing 

 leaf to an old-fashioned poke-bonnet (Figures 8 and 9, Plate II). In Figure 8 

 part of tlie sheath has been removed to show the conical character of the 

 interior. The tip of the growing leaf coming in contact with the apex of 

 the inner cône is deflected towards the slit. 



The differentation of the leaf blade from the rest of the leaf can be 

 readily seen in the very young leaves as a groove which runs parallej 

 with tiie long axis of the 'Anlagen' for the leaflets (Figures 1, 2, 3, 4, 5, 

 Plate 1 and Figures 8, 9, 11, 12, 13, 14, Plate 11). In the juvénile leaves 

 this groove is horizontal and in the mature leaves it is vertical or slightly 

 oblique. This groove is seen before any of the leaflets are visible on the 

 exterior of the leaf blade. The furrow marks the boundary between rachis 

 and the rest of the leaf consisting of pétiole, sheath and base. 



Up to the présent nothing new has been added to the development 

 of the palm leaf other than a description of the processes that go on in 

 the newiy formed leaf of the oil palm. The stages which follow upon 

 thèse are in the opinion of the writer, the critical ones. Differentiation of 

 a pronounced character, at least visible differentiation, begins in the third 

 leaf from the growing point. As has already been pointed out, the third 

 leaf from the growing point has been differentiated into sheath, pétiole, 

 base, and leaf blade. Leaves in this stage, dissected out, show no outward 

 évidence of differentiation going on within the leaf blade. It is only in 

 prepared material that the changes can be observed. 



Eac/i leaflet arises from a mass of cells within the leaf blade and the 

 indications point to their origin from single cells which are the ^Anlagen' 

 for the leaflets. Figure 37, Plate V shows the outermost leaf eut in a plane 

 which allows several of the 'Anlagen' to be seen. In this stage of deve- 

 lopment the 'Anlagen' can be seen as aggregates of cells, or cushions of 

 cells, which are in an active state of division. As thèse aggregates 

 continue to add on more cells they push the cells above ahead of them 

 and this pressure exerted by thèse 'Anlagen' gives a wavy appearance to 

 the layers of cells above them. A more detailed study of such an aggre 

 gâte of cells is seen in Figure 38, Plate V. The aggregate of cells in 

 this section is seen in the form of a more or less irregular circle, the center 

 of which is occupied by a somewhat larger cell. The cells surrounding 

 this larger one are in various prophase stages suggesting that a very active 

 division is taking place. The outermost layer of cells, more or less cubical 

 in form, is the upper epidermal layer of the young leaf blade. The next 

 layer inward is also composed of cubical cells. The cells of thèse two 

 layers are actively dividing. The cells of the lower epidermis are irregular 

 although they too are actively dividing. The gênerai impression is that thèse 

 'Anlagen' originate from single cells arising at the same level, cuttingoff 

 cells toward the periphery of the leaf blade. The active division of the cells 



