18 THE PALM-STEM. 



nearer to the centre the vascular bundle lies, the more 

 the liber is diminished in mass, till at last it displays only 

 a very thin crescent, while the size of the woody mass 

 increases in the inverse ratio, the smaller vessels lying at 

 its inner side increasing in number. The bundle of 

 proper vessels enlarges in similar proportion to those of 

 the woody mass. The softness of the whole vascular 

 bundle increases with the diminution of the mass of the 

 liber, because the liber alone contains the thick-walled 

 elementary organs. 



Similar changes in the structure of the vascular bundle 

 are met with, when it is dissected out from the stem and 

 examined in different parts. In this way we may not 

 only obtain, by comparison of transverse sections of one 

 and the same vascular bundle, a survey of the changes of 

 its size and structure which leaves no room for doubt, 

 but we may detect more readily than in the cross section 

 of an entire stem, the changes which the vascular bundle 

 undergoes in its way from the centre of the stem to the 

 base of the leaf.* 



These changes are as follows : the nearer the vascular 

 bundle approaches to the leaf, the more the liber-mass 

 diminishes in size and the woody portion increases, a 

 great multiplication of the vessels of the latter being con- 

 nected with this, these, however, considerably decrease 

 in size. In the vicinity of the point of emergence from 

 the stem, a division of the vascular bundle into several 

 (up to six) portions already begins to be effected, this 

 taking place in such a manner, that small bundles of liber 

 appear on the outer borders of the woody portion, at its 

 posterior and lateral surfaces, behind which, and at some 

 distance higher up, are found the rest of the systems 

 (wood and proper vessels) belonging to a perfect vascular 

 bundle, so that the entire vascular bundle consists of a 

 circle of smaller bundles, which all have their woody por- 



* What relates to these two methods of investigation is not a translation 

 of the original text, for the latter referred specially to the illustrations here, 

 and therefore would be incomprehensible without them. (H. v. Mohl.) 



