YampOLSKY: Study of OU palni. 117 



of the remainin<^ tissue keeps pace for the time beinj^ with cell division 

 in the 'Aiilagen' so tliat the developing leaflcts do not in this stage of 

 development peiietrate beyond the other cells. They do however, as we stated 

 above because of the appHcation of pressure at regular intervais, give a 

 wavy appearance to the cel! tissue directiy above them. 



In a true longitudinal section of a leaf blade the iiuiiibér of visible 

 leaflet 'Aiilagen' would be multiplied. It is aiso quite évident, however, that 

 not ail the 'Anlagen' arise simultaneously. New ones are added basifugally. 



Differentiation of tissue goes on rather early in the oil palm leaf. 

 In the third leaf from the growing point the bast cells and bundle cells hâve 

 begun to elongate and they can be seen in what is to be the base and 

 pétiole of the leaf. The growth of the 'Anlagen' goes on upward and 

 to the sides, apparently also differentiation begins to occur, for in the very 

 next stage, in the next following leaf, a definite epidermal tissue marks 

 the périphéries of each growing leaflet. That is seen in Figures 39 and 40, 

 Plate V; the wavy line of cells indicate the epidermal cells In this 

 fourth leaf from the growing point the leaflets are already in contact with 

 each other and they begin to exert latéral pressure upon each other. It 

 cannot be overemphasized that during the development of the leaflets they 

 are enclosed in the tissue of the leaf blade and although marked growth 

 and differentation has taken place in the leaflets, the leaf blade as a whole 

 shows no outward indication of that fact. Figures 39 and 40 are différent 

 sections from the same leaf. Figure 39 is a eut through the tipof the leaf 

 together with three developing leaflets; the split to the right of the drawing 

 is part of the line formed by the approximating edges of the two halves 

 of the leaf blade, such as one sees at the tip, for example in Fig. 12, Plate 11. 

 Hère we see the distinct character of the tissue surrounding the leaflets. 

 The cells are somewhat larger and longer and in Figure 40 they are seen 

 with their long axes running in a différent direction. This stage is impor- 

 tant in view of GOEBEL, ElCHLER and Deineqa's assertions that the 

 'Haut' develops secondarily after folding has occured. 



In Figure 41, Plate V we see a section through a leaf in still a later 

 stage of development. This section has been eut so that it is more or 

 less tangential, showing the ends of several developing leaflets. This section 

 is interesting since it shows the character of the cells surrounding the 

 leaflets. Thèse cells are larger, the nuclei smaller in comparison with the 

 rest of the cell. 



More striking are the leaflets shown in Figure 28, Plate III. Hère a 

 section has been eut through a leaf showing at least twelve developing 

 leaflets pressed closely against each other and enclosed within the tissue 

 of that half of the leaf blade {see also Figure 22, Plate III, leaf HH). This 

 section did not pass through the leaflets to show that splitting within the 

 leaflets had already begun. Actual splitting, as we shall see, begins even in 

 an earlier stage. It is in such stages that the évidence against the folding 



