THE PALM -STEM. 11 



form a perfectly regular tissue where the fibrous bundles 

 lie far apart ; in most cases the regularity of their arrange- 

 ment is destroyed by the cells lying next the vascular 

 bundles having their broad side, or more rarely their 

 narrow side, directed towards the vascular bundle, in 

 which latter case a stellate figure is formed round each 

 bundle (Leopoldinia pulchra). 



In that layer of the stem in which lie the thick, hard 

 vascular bundles, the cellular tissue becomes compressed 

 into thin lamellae, from the vascular bundles lying very 

 densely crowded here, and by their mutual pressure fre- 

 quently (especially in cylindrical stems) forcing them to 

 assume an angular figure ; these lamellae indeed have a 

 very variable direction according to the form of the vas- 

 cular bundle, but taken as a whole, run from without 

 inward, since the vascular bundles mostly exhibit a form 

 compressed on both sides. The cells are also here trans- 

 versely expanded in the direction of the lateral faces of 

 the vascular bundles, and so much the more, the nearer 

 they lie to the vascular bundles ; therefore they have in 

 the cylindrical stems, in which at most only 1 to 3 rows of 

 cells lie between every two vascular bundles, a very much 

 elongated form, while in other stems this only occurs 

 from accidental approximation of vascular bundles, and 

 the dodecahedral form of the cells reappears in all places 

 where the vascular bundles lie further apart. In propor- 

 tion as the cells assume a transversely extended form, the 

 superposition in perpendicular rows becomes converted 

 into an arrangement in horizontal rows, so that the cel- 

 lular tissue assumes the so-called muriform character. 

 In many Palms, e. g. Cocos botryopliora, the outer vascular 

 bundles stand behind one another in radiating rows, so 

 that broad strips of cellular tissue penetrate from 1 to 3 

 lines deep into the stem in the form of medullary rays. 

 In these strips, the cells exhibit lateral expansion parallel 

 to the surface of the stem. 



The cells of this layer almost always have much thicker 

 and harder walls than those of the fibrous laver and the 



