396 II. von Mohl on the Cambium-layer 



verge. This condition remains exactly the same, whether the 

 apex of the stem be drawn out conically, flattened, or depressed. 

 Whether the vascular bundles are all subsequently arranged in 

 a cylinder under the rind, or whether, as in the Palms, they run 

 inwards towards the centre of the stem, has nothing at all to do 

 with the longer or shorter state of the internodes of the stem, 

 but depends solely upon the difference above described, whether 

 the cambium-cone continues to form parenchyma outside the 

 vascular bundle or not. This does not take place in Dicotyledons 

 with short internodes, as in Sempervivum, because it is not 

 in accordance with the growth of Dicotyledons, while, on the 

 other hand, it occurs in Monocotyledons with elongated inter- 

 nodes. The curved course of the vascular bundles of the latter 

 from the leaf inwards to the centre of the stem, and from this, 

 again, outwards and downwards to the periphery, was indeed 

 discovered by me, in a hollow-stemmed Palm with long inter- 

 nodes. Schleiden is altogether incorrect (ed. 3. p. 158) in the 

 detailed exposition of the proofs of the peculiar mode of vegeta- 

 tion which he ascribes to stems with long internodes, — that in 

 them, for instance in the Grasses, the vascular bundles lying in 

 one internode do not originate seriatim from within outwards, 

 but are developed and perfected simultaneously. Examination of 

 the terminal bud of a large Grass, for instance Arundo Donax, 

 shows most distinctly, as indeed was already well known to 

 Moldenhauer, that the outer vascular bundles originate much 

 later, and occur in the still completely cambial condition while 

 the inner already possess spiral vessels. 



Just as little can we approve Schleiden's representation of the 

 growth of stems with short internodes and a short bud-axis ; for 

 he here derives the vascular bundles, not from a common cam- 

 biumcone embracing the whole axis of the bud, but from a 

 series of numerous successively-formed, funnel-shaped, hollow 

 cones, stuck into one another, and with free margins. It is self- 

 evident that this idea is decidedly incorrect, if applied to short- 

 jointed Dicotyledonous stems, for instance to a fleshy Euphorbia, 

 a Sempervivum, &c. : for the stems are constructed in every re- 

 spect in the same way as the long-jointed; audit has no influence 

 upon the mode of development of the individual internode and 

 its vascular bundles, whether this grows in the longitudinal 

 direction for some time after its emergence from the condition 

 of a bud, by cell-development and expansion, or whether this pro- 

 cess occurs only in a slight degree. We might be more inclined 

 to countenance this notion in reference to the development of 

 Monocotyledonous stems, since in these one cambium-cone is 

 certainly formed over another ; but the matter takes place in a 

 different way from that described by Schleiden, and exactly in 



