230 
PROFESSOR W. C. WILLIAMSON ON THE ORGANIZATION 
these layers, as well as along the fewer lines indicated by the thickened peripheral 
margin of each primary disk. 
Fig. 46 is another transverse section from the same locality as the last, enlarged 4-| 
diameters. It is peculiar inasmuch as it is one of the very few examples of a Dadoxylon 
in which I have seen concentric lines of growth in the woody zone. Two or three of 
these lines are sufficiently distinct. The more peripheral ones are more faintly marked. 
There yet remains to he considered some peculiar divergent elements which exist in 
several of the specimens. These are best seen in the transverse sections figs. 44 & 46. 
In fig. 44, g, g, two narrow vascular bundles arise from near the innermost margin of the 
woody cylinder, and move in nearly parallel lines towards the periphery. Fig. 47 repre- 
sents a portion of the vertical section fig. 45, enlarged fifteen times, but from a part 
not represented in the latter figure ; we here see, at g , one of the bundles corresponding 
to those of fig. 44, g, g, intersected almost, though not quite, radially. We here discover 
that the vessels V, bending outwards to form the bundle g , are derived from the inner- 
most layer of the woody cylinder b. This orientation of these small bundles from the 
innermost layers of the wood is suggestive of their primary relation to leaves rather 
than to branches. A similar bundle departs from the interior of fig. 43 near g. Fig. 46 
exhibits two of these pairs of bundles at g , g. This example is valuable, because it 
demonstrates, through their angle of divergence, that these bundles do not proceed to 
distichous peripheral appendages. Fig. 48 is part of a tangential section of the spe- 
cimen fig. 44, enlarged 15 diameters. It has intersected two of these bundles at right 
angles to their direction, and is interesting as demonstrating their perfect twin-like 
character. The elementary tissues in the two bundles of this section are destroyed by 
mineralization, but the other examples clearly show that, when preserved, they consist 
of the ordinary discigerous fibres of the woody zone. 
Fig. 49 is part of a tangential section of the ligneous zone of the Coalbrookdale 
branch, figs. 33-40, enlarged 62 times. The section was made close to the medulla. 
In fig. 38 we see a number of cells, f, identical with those of the medullary rays, and 
which, like the latter, doubtless constitute outward prolongations of the medulla. The 
fibres which are in contact with these cells, whether coming from above or from below, 
have their regular arrangement disturbed, so as to be cut through by the section ; they 
become suddenly deflected, to make way for the cellular rays pursuing their horizontal 
course towards the periphery. 
In the specimen, fig. 42, 1 find a solitary bundle given off from the inner margin of the 
ligneous zone at g ; and in the vertical section of the same example, fig. 43, there is near 
g a bundle, the position and course of which correspond exactly with that seen in fig. 47. 
I find no traces of these bundles near the outer margins of such sections of large branches 
as I possess *. 
The question arises, what is the destination of these bundles 1 On making a series of 
sections of the large-leaved Araucaria imbricata and of Taxus , I find in their young 
* This bundle is not distinctly shown in the figure. 
