THE PALM-STEM. 19 



tions directed toward a common centre, and by the simple 

 separation of these subdivisions, it becomes decomposed 

 into just so many bundles containing all the essential parts 

 of the vascular bundle. 



From the character of the vascular bundle, as above 

 described, follows incontrovertibly the total falsity of the 

 generally received opinion, that the thicker and firmer 

 vascular bundles lying in the outer parts of the stem are 

 the older and lignified, and that the softer, lying in the 

 middle, are the younger, not yet come to their complete 

 development. 



Modifications of the Structure of the Vascular Bundle in 

 various Palm-stems* 



Although the structure of the vascular bundle exhibits 

 a common type in all Palms, modifications occur in the 

 different species. 



In the cane-like stems, the liber of the outer hard 

 layer of the stem displays a very considerable develop- 

 ment ; toward the centre it, indeed, diminishes again in 

 volume, yet still retains a moderate size, and since the 

 the vascular bundles are not very distinct from each 

 other, the middle of the stem possesses tolerable solidity. 



In the cylindrical stems, the liber of the outer layers ex- 

 hibits the greatest development that occurs in the Palms, 

 into a mass often elongated in the direction from within 

 outwards ; in the middle of the stem the vascular bundle 

 acquires an herbaceous softness, partly through the dimi- 

 nution of the liber-bundle, partly through the walls of 

 its cells becoming so very thin, that in a cross section 

 they resemble parenchyma-cells. 



In the cocos-like stems the liber only increases slowly 

 in the passage of the vascular bundle from the fibrous 

 layer toward the interior, and does not attain any con- 

 siderable size ; the vascular bundles of the outer parts of 



* This portion consists of extracts, since the detail in the original referred 

 to the illustrations. (H. v. Mohl.) 



