52 
PROFESSOR W. C. WILLIAMSON ON THE ORGANIZATION 
have obtained one such section, represented in Plate V. fig. 27. In it we find a branch 
(x) projecting through the bark from the exogenous vascular laminae which radiate from 
one arm of the central triangle. It appears as if most of the small vessels of one of 
the three segments radiating from these several angles were more or less deflected into 
this divergent appendage*. I am not quite sure that any of the central vessels of the 
triangle take any part in the new structure ; but I have little doubt that the smaller ones 
constituting the extremity of the angle do so, since I find them to be distinctly deflected 
in the direction of the new growth. It is obvious that the vascular axis of this branch 
consists of a mass of vessels, some of which may be derived from the extremity of one 
angle of the central triangle ; but the greater number of which certainly consist of the 
small vessels of the exogenous layer, which here radiate in converging lines from that 
angle. We thus obtain our first glimpse of the special use of the three alternating 
groups of small vessels seen in transverse sections of these stems, viz. to afford the vas- 
cular supplies required by some of the lateral appendages f. If this is a correct inter- 
pretation, there arises for further inquiry the interesting question whether o*r not the 
verticillate lateral branches are grouped with angles of divergence of 120°; or, in other 
words, are they arranged in ternate verticils, as appears to be most probable 1 I have 
found no example like the one just described amongst my Oldham specimens. But this 
is doubtless accounted for by the fact that nearly every one of the latter, in connexion 
with which I have found the nodes, have been young terminal twigs, as indicated by the 
regularity with which the leaf-bases remain in situ : consequently all their lateral buds 
were as yet undeveloped. 
The bark of Plate V. fig. 27 obviously exhibits the innermost layer (g) in a contracted 
or compressed condition, whilst the outer one ( k ) is of fully double the thickness of that 
seen in the large stem, Plate IV. fig. 21. This enlargement corresponds with what we 
have already seen in the transverse section of the nodal disk in Plate III. fig. 16, and 
leaves no doubt on my mind but that the former is also a nodal section. There is no 
doubt, therefore, that the Burntisland plants exhibited the same nodal expansion of the 
bark that we find in the Lancashire type. It will further be observed from Plate V. 
fig. 27, g', that the inner and middle barks accompany the branch in its outward course, as 
might have been anticipated, supposing my interpretation of this structure to be 
correct. 
After combining the facts which I have enumerated, I have no doubt that these 
* It is interesting to find that M. Renault has discovered solitary branches in some of his Autun specimens 
occupying exactly this position. He says respecting them, “ Les rameaux que j’ai eu occasion de rencontrer 
encore adherents a la tige etaient solitaires sur leur articulation.” “ Ceux que j’ai observes etaient toujours 
orientes de fagon a etre contenus dans le plan de l’un des angles saillants de l’axe central de la tige ” (Joe. cit 
p. 8, plate i. fig. 3). — February 9, 1874. 
f M. Renault’s discovery of the position and origin of the true foliar bundles already referred to (pp. 45 & 48) 
leaves no room for doubting that these deflected laminae have been connected with a lateral branch, and not 
merely with leaves, since we have seen that the exogenous laminae do not contribute to the formation of the 
merely foliar bundles. — February 9, 1874. 
