70 THE PALM -STEM : 



formed in a different way from those of the Dicotyledons, 

 originating from ramification of the old vascular bundles, 

 while in the Dicotyledons the new fibres are deposited 

 between the bark and the ends of the older fibres which 

 emerge into the leaves, this conclusion is not justified 

 by the anatomical character of the Dicotyledonous stem, 

 since it leaves wholly out of sight the fact, that in very 

 many Dicotyledons the lower end of some of these vascular 

 bundles stands at least in quite as close organic connexion 

 with other vascular bundles as in the Monocotyledons; so 

 that the younger vascular bundles have much resemblance 

 to those of the Fern-stem in respect to the arrangement 

 and union. 



Lestiboudois devoted especial attention to the roots of 

 the Monocotyledons ; from the examination of them he 

 drew two conclusions : 1 . Their vascular bundles are not 

 formed by gradual elongation of those of the stem. 

 2. Their growth is endogenous, for their vascular bundles 

 are perfected from without inward, and new vascular 

 bundles originate in the interior of the root. 



Schleiden (Wiegmann's Archiv, 1839, p. 220; Grund- 

 ziige der wiss. Bot. i, p. 220) directs attention to the 

 point that the vascular bundles are developed in a similar 

 manner in the Monocotyledons and the Dicotyledons, the 

 part turned towards the interior being that which first 

 originates, and he considered it to be the only thorough 

 distinction between Monocotyledons and Dicotyledons, 

 that in the latter the formation of new elementary organs 

 proceeds indefinitely in the cambium-layer of the vascular 

 bundle (whence he calls these vascular bundles unlimited}, 

 while in the former this development ceases at a certain 

 epoch (limited vascular bundles), and the elementary 

 organs of the cambium-layer assume the peculiar form in 

 which I have described them under the name of proper 

 vessels. With regard to this distinction, the knowledge 

 of the facts on which it depends is not new, only the ex- 

 planation, in so far that Schleiden quite correctly explains 

 the continuous deposition of new layers of wood in the 





