of the Stem of the Phanerugainia. 397 



the same way as in a stem with cylindrical and elongated inter- 

 nodes, whose terminal bud is really just as conical as that of a 

 short-jointed stem. The cambium -cylinder of a Dicotyledonous 

 stem, which is constantly transformed on its inner side into 

 woody layers and cells of medullary rays, and is constantly re- 

 newed on its outer side by development of cells, consists at dif- 

 ferent epochs of totally different cells, and occupies also a different 

 place ; but it remains always essentially the same, and no one 

 would represent the matter by saying that in the course of time 

 a more or less considerable number of distinct, concentric cam- 

 bium-cylinders had been formed. Just as little ground, how- 

 ever, exists, if we do not admit this view, for regarding, with 

 Schleiden, the development and renovation of the conical cam- 

 bial mantle of the conical bud as the product of distinct and 

 successive funnel-shaped cambial mantles, sticking into one an- 

 other, with their edges free. The latter assumption rests upon 

 a totally mistaken notion. Schleiden^s view, that the bud pos- 

 sesses a distinct cambium-mantle in each internode, has no 

 foundation in fact ; one cambium-region is commion to them all, 

 and only its higher and lower zones correspond to the individual 

 internodes. No trace exists of a free margin of a cambium- 

 mantle belonging to a single internode ; but the zone of cambium 

 corresponding to each internode forms the immediate continua- 

 tion of the cambium-zone of the next internode below, just as 

 in cylindrical stems. When, with the advancing development of 

 the bud in the upper portion of the cambium-mantle, the inner 

 part is transformed into vascular bundles and parenchyma, and 

 its outer part is renovated by development of cells, and in this 

 way a new and more externally situated cambium-mantle is 

 formed, this renovation occurs in a degree continually decreasing 

 downwards to the place where the production of new cells en- 

 tirely ceases, and the cambium-mantle passes into the now no 

 longer productive cambial cylinder of the lower part of the stem. 

 Hence the growing downwards of an upper cambium-mantle 

 over the free margin of that belonging to a lower internode, 

 in stems which are thicker above, is out of the question, since 

 no such free margin exists. If a stem becomes thickened into 

 an inverted cone, this arises from a greater number of elementary 

 organs being developed in the upper internodes; but this does 

 not generally take place suddenly, and it is not that an upper 

 internode grows down over the periphery ; for the lower inter- 

 node takes part in the development of the upper, becoming 

 inversely conical and passing gradually into the latter. 



No less erroneous is the view that the cambium-cone corre- 

 sponds to an internode, and that consequently the newly-formed 

 vascular bundles run from the circumference of the internode to 



