Pomona College Journal of Economic Botany 



415 



This is proved by the fact that when a palm loses its central shoot no new 

 roots make their appearance, although the more external leaves may remain 

 alive and retain their functional activity for several years afterwards. 



From what I have observed, the new emission of roots happens only 

 when the newly formed leaves begin to expand. This exposition of the mode 

 in which new roots in palms are emitted, is corroborated by what takes 

 place when, for example, we desire, for horticultural purposes, to transplant 

 a palm (a Phoenix or a Cocos, for instance). We are then obliged to cut 

 away the greater part of its roots, and also the older, but not yet quite 

 functionless, leaves. We can then see that the new roots make their way 

 externally to and above the old ones, on the periphery and at the base of 

 the trunk, as soon as the newly formed leaves begin to expand. 



From all I have now said, it seems to me certain that a correlation 

 exists between the emission of new leaves and that of new roots. This 

 parallelism apparently exists, also, in the number, form, and disposition of 

 the vascular bundles of the roots, and in the form, number, and disposition 

 of the primary nerves in the primordial leaves. The existence, therefore, 

 of an uninterrupted continuity between the vascular bundles descending 

 from the leaves and the new roots, appears extremely probable ; it is, indeed, 

 an unavoidable consequence of the necessity of a physiological connection 

 between the hypogean and the aerial system. 



The result of this continuity of the vascular bundles descending from 

 the new leaves down to the base of the trunk is that we find at every new 

 vegetative period an increased number of newly formed vascular bundles; 

 these must not, however, be regarded as elements of secondary growths, but 

 as true primary formations striving to intercalate themselves among the pre- 

 existing vascular elements. An interstitial augmentation of the number of 

 vascular bundles thus takes place, which in the case of those palms whose 

 stems are unable to distend their outer or cortical coatings (arecoid, arund- 

 inaeeous, calamoid trunks) increase their internal solidity; while those trunks 

 whose tissues are of a soft nature and which, on account of the loose structure 

 of the peripherous parts of their woody cylinders, are susceptible of distension, 

 (which is especially the case in palms of the cocoid type), will increase in 

 girth. In this latter kind of trunks even the fundamental parenchymatous 

 tissue may find room for cellular multiplication. If, therefore, in any 

 transverse section of the lower and thickened part of a palm stem new, 

 young, vascular bundles occur, I am inclined to suppose that this fact is 

 not to be attributed to a neoformation process, but to an extension in length 

 or to a division of the new bundles derived from, the nearly expanded leaves 

 in their tendency to produce new roots. Of these bundles, perhaps only a 

 portion reaches the base of the trunk to produce bulbous enlargements 

 and cause the emission of new roots there; other portions may be arrested at 

 different levels and contribute only to the solidity of the woody cylinder; 

 or, at times and under certain circumstances, they may force their way 



