1 14 BULLETIN JARD. BOT. BUI TENZORG, SÉRIE III, VOL. V. LlVR. 2. 



The transition from the small leaf to the adult, one, in some cases over 

 4 meters in length, is, however, graduai when one considers that it takes 

 from 5 to 7 years for the maximum develppment to occur. The massive 

 mature leaf with its long rhachis and many leaflets, with its pétiole flexible 

 and strong, tapering into a fine line towards the free end and at the opposite 

 end merging into the leaf base and enveloping sheath is distinctly, in its 

 outward appearance, a completely metamorphosed organ when compared 

 with the juvénile leaf. The serrated edges of the pétiole of the divided 

 leaf in the form of sharp teeth together with the sharp spines, a resuit of 

 the abortion of the leaflets formed at the base of the leaf blade, are entirely 

 lacking in the very first leaves. 



The length of time that it takes a mature leaf to develop from its 

 initial formation to its émergence and unfolding can be approximately 

 determined. This is done by determining the average number of leaves that 

 are produced per year per tree. BuCHER and FiCKENDEY P) state that in 

 the Kamerun 12—20 leaves are produced per year. Maas (-") estimâtes the 

 average in Sumatra to be 20—24. A five year old tree growing in the 

 „Cultuurtuin" at Buitenzorg showed, exclusive of the crown leaves, 60 leaves 

 in varions stages of development counting as the oldest leaf the one which 

 vvould hâve unfolded next in the normal course of events and the youngest? 

 as the last leaf developed from the growing point. On the basis of 20—24 

 leaves produced annually, it takes from 2'/2 to 3 years for a leaf to develop 

 beginning from the time that it is differentiated from the growing point 

 to the time that it is ready to émerge. » 



Investigations. 



Dissecting out the growing point of the plant offers no difficulties. 

 This can readily be done with the aid of a dissecting microscope. Figure 29 

 plate IV represents the growing point dissected out from a two year old 

 plant. Seen from above the growing point is ovoid in shape, the surface 

 convex and the highest point in this view is somewhat eccentric, desig- 

 nated by the somewhat heavier shading. Presumably the next leaf is to be 

 deliminated from that région. Figures 31 and 32 taken from prepared slides 

 show the growing point, or perhaps better the growing hémisphère, to be 

 of the same character as the one in the living condition. 



in a longitudinal section, Figure 23, Plate III and Figure 37, Plate V, 

 the more or less hemisperical condition of the growing région is seen. The 

 cells of this growing région are cubical in form ; the nucleus occupies the 

 greater part of the volume. There is a periclinal arrangement of cell layers 

 in the growing région, usually three or four layers Beyond thèse layers — 

 that is towards the interior of the growing région — there appears to be no 

 regular arrangement of the cells, although they are distinctly embryonic in 

 character as evidenced by the active cell division that is going on. The 



