68 Prof. Mey(?n\s lieport of the Progress of 



is 4t placed to the axis of the stem, and the lower to the peri-* 

 phery. 



In the greater number of dicotyledons the isolation of the 

 vascular bundles is retained, and consequently the integrity ot 

 the original proportions only up to a certain period. Ac-r 

 cording to the genera each bundle ends more or less quickly, 

 in such a manner that they arrange themselves with their sides 

 upon each other, and the circle of vascular bundles becomes 

 now a firm tube, which is traversed solely by radial laminae, 

 formed by series of horizontal cells. The new bundles, which 

 continue to be organized, after this tube is closed, increase its 

 size, so long as the vegetation of the year continues. If, there-? 

 fore, we divide the apex of a young germ, we see that the vas- 

 cular bundles which pass into the leaves constantly proceed 

 from the internal layer of wood. These fibrous vascular 

 formations were distinguished by Girou de Buzareingues ac- 

 cording as they belonged to the leaves of the young germ, or 

 to the buds which are developed in the angles of those leaves. 

 He showed that these buds, notwithstanding their apparently 

 more interior position to that of the leaves, rise out of the 

 summit of a more projecting medullary production; and that 

 their vascular bundles, allowing a passage to those of the 

 leaves, descend on the exterior side of the first fibrous body. 

 Both of the two zones, therefore, are formed by several small 

 concentric layers; those of the external ring are always ar- 

 ranged so that those that Jire for the most part peripherical 

 belong to the lowest buds ; the most interior, on the contrary, 

 to the highest ones. Thus it is also with the central zone in 

 annual plants in the shoots of the Rhizocarpcu, and for the 

 greater part also in the new shoots of trees ; but in some of 

 the latter the arrangement is just the reverse, by which the 

 fibres of the upper leaves are exteriorly over the others, 

 ^nd those, above all, nearest to the central point, are those 

 which belong to the inferior leaves. The column of pith in 

 this c«nse takes an obverse conical form, while it has that of a 

 straight cone in the first instance. Mohl does not distin- 

 guish these two cases, nor the two zones as distinct and 

 exclusive productions of the leaves and of the buds. He 

 concedes tliat in the aj)ex the lecent fibres are organized in the 

 interior of the older ones ; and he brings forward various data 

 in order to overthrow Alph De Candolle's explanation of the 

 crampons (?) (Wurtzcl-fasscns)^ which would jireserve, on that 

 ground only, to the monocotyledons the name of Endogens. 

 But in the inferior parts, heib\nid in the dicotyledons a nature 

 so <Jifierenl, that it would serve as the most certain character to 



