122 Bulletin jard. Bot. Buitenzorg, Série III, Vol. V. Livr. 2. 



can be seen adhering to the edges. It is represented by the dotted area to 

 the right of the upjDermost leaflet in Figure 15, Plate. 11. Uiider the microscope 

 thèse cells are recognised as being decidedly différent from the cells of the 

 leaf tissue, due to their larger size, their irregularity as a resuit of tearing 

 duriiig the process of slit formation, and by their thicker walls. Thèse cells, 

 persisting as they do, tend to keep the leaflets together and give them the 

 appearance of having been folded together from a commoii leaf blade. 



if we examine the distribution of the slits we find that there are twice 

 as many on one side as on the other side, due, of course, to the fact that 

 the splitting of the individual leaflets occurs uniformly on one side. in the 

 upright position of the leaf thèse are on the outside since the morphologically 

 upper side of the leaf is turned inward and only upon unfolding of the 

 leaf and reflexing of the pétiole does the morphologically upper side come 

 to lie in its true position. That means, of course, that the midribs of the leaflets 

 are formed on the inside of the developing leaf and later are found on the 

 upper side of the leaf. 



When the leaflets ultimately separate and the halves of the leaflets unfold 

 along the split edge the force exerted in the process actually tears them apart 

 with the resuit that the still persisting enveloping tissue gives a ragged 

 appearance to the edges of the leaflets. As we hâve already pointed out, the 

 development of an epidermal layer occurs almost simultaneously with the 

 splitting of the leaflet. 



In the oil palm, at least, there is no évidence for the assertion that 

 definite parts of the tissue degenerate to liberate the segments. AU the 

 évidence points to a mechanical tearing of a persisting tissue — a tissue which 

 is thrown off at a late stage of development. 



Juvénile leaves, 



At the beginning it was stated that the young oil palm, like ail palms, 

 shows an undivided leaf and that the transition from the undivided leaf to the 

 fully divided leaf is a graduai one. The first leaves are lanceolate and, as a 

 rule, the leaves show a divided character at the beginning of the sixth month. 

 In Figure 106, plate XII a young seedling, still attached to the seed, shows 

 the lanceolate leaves. There appears to be a strongly developed mid-rib and 

 no indication of splitting. Another such leaf is seen in Figure 7, Plate I. It will 

 be observed that at the base of the leaf, just above the tubular sheath, the 

 ribs give a fluted appearance to the leaf blade. 



The juvénile undivided leaf in its origin does not differ markedly from 

 the fully mature leaf. It arises as a blunt protubérance from the side of 

 the growing région. It then grows over the growing point developing 

 into a bonnet-like structure. Differentiation of leaf blade begins by the 

 formation of an horizontal furrow followed by the formation of segments 

 in the very same manner as we hâve described for the mature leaf. 



