APPENDIX. 51 



imbedded in it ; in the inner vascular bundles, the proper vessels are some- 

 times wholly surrounded by the liber-tubes. The outer vascular bundles 

 are often confluent in pairs, in which case the compound bundle possesses 

 four groups of proper vessels, or, from the confluence of one pair, frequently 

 only three. 



The parenchyma of the root consists of thin-walled, somewhat elongated, 

 porous, parenchymatous cells, which in many places leave irregular spaces 

 between them. Around the stars formed by the vascular bundles, separated 

 from them by a few rows of cells, runs a darkish line, formed by cells with 

 rather thicker walls. Scattered through the whole root, and accumulated in 

 especial quantity in its outer layers, lie evascular, fibrous bundles, the outer 

 of which are often blended together, and are composed of thick-walled, prosen- 

 chymatous cells ; in the middle of those situated more internally, occur from 

 one to two thin-walled cells, which probably belong to the system of proper 

 vessels. I can state nothing concerning the connexion of these fibrous 

 bundles with the stem, as I had no opportunity of examining the latter. 

 These roots of Iriartea are clothed with short thorns, which are to be looked 

 upon as abortive lateral branches, and have their origin from the vascular 

 bundles of the main roots. 



Different as this root appears to be from those of other Palms, yet it is clear 

 that its organization agrees with that of the latter in many respects, since 

 most of the characters by which the vascular bundles of the roots are dis- 

 tinguished from those of the stem, occur in the root of Iriartea, as well as 

 in the roots of other Palms. The reversed position, which is exhibited by 

 the vascular bundles of the roots of Iriartea, corresponds to the circum- 

 stance met with in other Palm-roots, that the cells lying behind their 

 vessels likewise have the form of prosenchymatous cells. In both varieties 

 of the root the large vessels lie furthest inward, the small ones externally ; in 

 both, the proper vessels form special bundles not inclosed between the wood 

 and liber. 



APPENDIX. 



It will not be unfitting to append to the preceding 

 description of the Palm-stem, a short account of the 

 works on this subject, which have appeared since it was 

 first published.* 



* My purpose here is not an enumeration of all the observations on this 

 subject which have appeared since my Anatomy of Palms, but only an 



