THE PALM-ROOT. 49 



rind ; the cells become larger ; the outer, at the same 

 time, acquire thickness in their walls, and form the coria- 

 ceous membrane above described. The epidermis is 

 composed of cells not elongated, but papilliform and 

 projecting. In the young root the rind is compact ; but 

 with the greater expansion of the root in thickness, and 

 the decrease of its juices, the cells separate from each 

 other in isolated, larger or smaller, irregularly scattered 

 places, and thus form irregularly distributed air-cavities. 

 The cells immediately surrounding the central body, con- 

 tain on their inner side transverse fibrous thickenings, 

 like many anther-cells. Isolated cells, scattered without 

 order in the rind, contain raphides. 



The lateral roots spring from the larger roots in the 

 same way as these do from the stem. A nucleus of cellular 

 tissue is formed between the rind and central body of 

 the main root, and in this are developed moniliform 

 vessels. On further enlargement, this nucleus breaks 

 through the rind of the root, and appears as a branch of 

 it. The moniliform vessels penetrate the central body of 

 the root, run in the most varied directions in the cellular 

 tissue situated between the vessels, and finally apply 

 themselves to the sides of the large vessels. In the lateral 

 root itself, the vascular tubes become more and more 

 elongated, and form, with a portion of the cellular tissue 

 which they inclose, and with the elongated cells by which 

 they are surrounded, the central body of the root-branch. 

 The most external layer of these elongated cells is blended 

 with the thick-walled cells surrounding the central body 

 of the main root ; while the more central, pith-like cells 

 of the lateral root are connected with the parenchyma 

 situated beneath these elongated cells. The rind of the 

 side root is, indeed, separated from these in the greater 

 part of its course through the rind of the main root, by 

 its epidermis and its outer layer of elongated cells ; but 

 both the elongated and the parenchymatous cells of the 

 rind of the side root are blended with the more internal 

 layers of the rind of the main root. 



4 



