120 Bulletin Jard. B ot. Buitenzorg, Série 111, Vol. V. Livr. 2. 



It is seen also to the right of Figure 16, Plate II, and a portion of a blade 

 with thèse leaflets held together by the strip is seen in Figure 17. Moveinent 

 in growth of either rhachis or leaflets will affect the position of ail the 

 leaflets that are held together. 



Figure 33, Plate IV is a cross section through a young leaf showing 

 three pairs of leaflets in cross section. At first sight it would appear that 

 folding of the respective halves of the leaf blade, as described by GOEBEL, 

 has occurred. That, however, is not the case. The careful dissecting out 

 of the varions stages of developing leaves shows that that is an erroneous 

 conception. The angular character of the leaflets is a resuit of mutual 

 pressure of. equally developing parts within a limited space. Figures 34 

 and 35 are somewhat later stages. Figure 35 shows the fairly undif- 

 ferentiated leaflets which hâve already split, held together in part by the 

 original enveloping tissue, the cells of which are seen running in a vertical 

 direction. This stage seen alone might iend argument to the assertion that 

 the "Haut" is a secondary development. 



In the young leaf which is to give rise to the mature leaf of the 

 5 year and older trees, the 130 to 160 pairs of leaflets are closely 

 packed together. Figure 18, Plate II is from a leaf of a five year old 

 tree. A cross section through the upper part of such a leaf would 

 eut through twelve pairs of leaflets. With the increasing growth of 

 the leaves the space relations change so that the older leaves hâve 

 more room for development and consequently the leaflets, as a resuit of 

 released pressure, lose their angular configuration (Figure 36, Plate IV). 

 It must always be borne in mind that thèse leaflets are still held together 

 by the tissue of the periphery of the leaf blade so that in a cross section 

 there is no apparent break between the leaflets. 



Where the enveloping tissue of the growing leaflets is less résistant, 

 the leaflets will ultimately break through. That occurs on the sides of 

 the leaf blade. The apices of the growing leaflets are held together by the 

 comparatively thick strip at the edge of the leaf blade which prevents, 

 for the time being, the séparation of the leaflets from the mother tissue 

 along that line. The tissue on the side of the leaf blade surrounding the 

 developing leaflets is comparatively thin so that very soon this tissue con- 

 forms to the outline leaflets due to the pressure of the several leaflets 

 and we hâve the ringed appearance of the halves of the leaf blade re- 

 calling the outer segmentation of the earthworm. Thèse are the "Wiilste 

 of Naumann (23) and folds of GOEBEL and ElCHLER. Figure 16, Plate II 

 shows the leaflets of one side of a blade in parallel arrangement. A larger 

 magnification of such leaflets is seen in Figure 17, Plate II. Where the 

 pressure from the enveloping tissue of the leaflets is released they take 

 on a rounded form. With the increased growth of the leaflets the résul- 

 tant pressure exerted on the sides of the leaf blade causes the tissue 

 between each two leaflets to tear and we hâve then the formation of slits which 



