124 Bulletin Jard. Bot. Buitenzorg, Série III, Vol. V. Livr. 2. 



separated from the rest of the blade. The later leaves show varions gradations 

 from the partially divided leaf to the one that is completely divided. The 

 dichotymoiis appearance of the end segments due to failure of several 

 segments to separate from one another continues well into the second year. 

 From thèse stages it can readily be seen that what appears to be a mid-rib 

 in the juvénile leaf is really not so. Yh\s mid-rib is morphologically 

 équivalent to the rachis of the mature leaf and is therefore a true rachis. 



The transit, on from a ianceolate undivided leaf to a divided or pinnate 

 one is very interesting to follow in the young stages. Changes of a pro- 

 found character take place in the young leaf. It is to be remembered that 

 the leaflets or segments in the juvénile leaf arise from a more or less 

 horizontal plane and those in the divided leaf from a vertical plane. In the 

 transition stages from the juvénile leaf to the mature leaf there is a shifting 

 of the plane of origin of the leaflets, so that it comes to lie almost in a 

 vertical position. Figures 4 and 5 Plate 1 shovi' such transition stages; 

 they also show an increase in the number of segments or leaflets. The 

 relatively wide strip still persists as well as the strongly developed tip. 

 The older leaves develop successively more leaflets and that means more 

 'Anlagen'. 



Figure 6 Plate I shows a young leaf taken from a seediing whose 

 unfolded leaves showed no segmentation. This young leaf when mature 

 would show at least 17 pairs of leaflets. With the increasing âge of the 

 plant, the leaves hâve more leaflets until the 5th to the 7th year, when 

 full maturity of the plant is reached. 



The striking altération of leaf form from an outwardly undivided to a 

 pinnate leaf, with the horizontal plane in which the segments ofthe former arise 

 going over into the more or less vertical plane in wliich the iatter leaflets arise, 

 has an interesting parailel in the manner in which fan leaves and pinnate leaves 

 arise. The fan palm leaf arises much in the same manner as the juvénile 

 leaf, in an horizontal plane whereas the pinnate leaf arises in a vertical plane. 



Sheath. 



The sheath of the oil palm leaf is a conspicuous and persistent organ. 

 It arises after the young leaf has been differentiated from the growing 

 point and after the horns of the crescent shaped structure hâve grown 

 around the next succeeding leaf ultimately enveloping it. Figures 29, 30, 

 31 and 32 Plate IV show varions initial stages in the development of 

 the ring. When the tips of the horns meet growth is deflected upwards 

 and the sheath, as such, begins to develop. Only the gross features 

 of development of the sheath hâve been followed in this study and it 

 is by no means a complète study of this organ. The forms of the sheath 

 in the later stages are shown in the several plates and they can be 

 recognized as such without further explanations. 



