YAMPOLSKY: Study of OU paLiii. 115 



nucieo-cytopiasmic relation in tlie cells of remoter parts tends more and 

 more to become equalized. The growing point is not stationary as one 

 can deduce from the ^/j. arrangement of the leaves. How tliis rytlimic 

 shiftiiig is broiight about is liard to say. The newest leaf arises as an 

 outgrowth or hook from the side of the growing région closely pressed 

 against tiie side. There seems to be a receding of the growing région 

 50 that the higiiest point in the growing région lies almost opposite to the 

 youngest leaf. This shifting in the growing point, tends also to raise the 

 growing région so that it always continues to maintain a definite level. 

 The growing région always lies at the bottom of a hollow or dépression, 

 always of course protruding above the lowest level of the hollow. Figures 

 22 and 23 of Plate il! which are longitudinal sections through a two year 

 old plant, bring out very distinctiy the relationship of the growing région 

 and developing leaves. As the plant continues to develop the oldest leaves 

 are thrown off and the growing région is shifted upwards so that in a very 

 old tree the growing région is not distantly removed from the leaf crown. 



The new leaf arises as a blunt hook-like protubérance from the side 

 of the growing point (Fig. 37, Plate V and Fig. 23 Plate 111). Viewed from 

 above it is in the form of a crescent (Figures 2Q, 30, 31, 32, Plate IV). 

 Growth goes on in several directions. The free ends of the crescent begin 

 gradually to approximate one another so that ultimately they unité, completey 

 encircling the leaf within. This portion of the developing leaf, as we shall see 

 later, gives rise to the sheath. As soon as the ends meet, growth in a circle 

 ceases. The ends coalesce and growth now begins upward. Simultaneousiy 

 with this growth in a circle, the blunt hook begins to grow upward and to the 

 sides so that very soon it has grown above the growing région bending 

 over it in the from of a bonnet. This is very well shown in Figure 37, 

 Plate V which represents a longitudinal section of the growing région and 

 the three youngest leaves. The outermost leaf of the three in longitudinal 

 section appears like a cône, the slit to the right showing where the leaf 

 blade and the sheath approach one another. In the next two leaves the 

 small protubérances to the right and to the left respectively are the 

 developing sheaths. Bearing in mind the ^/g arrangement of the leaves it 

 will easily be seen why a longitudinal section through a séries of leaves 

 gives so many différent aspects to the leaf. 



One can best visualize the subséquent processes of growth by imagining 

 a cône with an inverted T eut into the surface, the longitudinal bar of the 

 T reaching from the apex half way down and the horizontal bar half way 

 around. Now if the flaps were turned back somewhat, they would represent 

 the two parts of the leaf where the 'Anlagen' for the respective rows of 

 leaflets develop. The opening in the cône represents the opening through 

 which the apex of the next developing cône (leaf) appears. The disposition 

 of the leaves of an oil palm in a young stage may very well be likened 

 to a séries of progressively smaller cônes, the respective apices of which 



