ORGANIZATION OF THE FOSSIL PLANTS OF THE COAL-MEASURES. 695 
be well shortly to pass in review the principal specimens in which branching is shown, 
with special reference to the light which they throw upon this question. 
Branching of the Roots. 
Some examples of branched roots have been figured in previous memoirs,* while 
others are illustrated in the present paper (see photographs 6 and 7, figs. 6 and 8). 
Most of these specimens have no direct bearing on the question, for in some the 
branches, as well as the main root, have a distinct medulla,+ while in others both the 
main axis and the branches are rootlets, with little or no pith (fig. 8).t 
The specimen shown in photograph 6 is of considerable interest. Here the principal 
root is probably hexarch, and has a perfectly well-defined, though small pith, 8 to 10 
cells in diameter. Opposite two of the:protoxylem-groups branches are given off, both 
of which are cut sufficiently near their median plane to show the continuity of their 
primary xylem with that of the main axis. In one branch there is no sign of any 
pith ; in the other, one or two rows of parenchymatous cells can be distinguished. 
Such evidence is not conclusive, but the specimen certainly appears to show the bases 
of two rootlets, with little or no medulla, inserted upon a root, which, though small, 
has the typical internal structure of “ Astromyelon,” t.e., of the Calamitean root. 
Another specimen§ shows no less than four rootlets, in a tangential section of the 
main root, which, from its having distinct primary rays, was in all probability of the 
medullate type. 
Plate 16, fig. 6, shows a tangential section (from another specimen) through the 
wood of a relatively main root, with a branch seen in approximately transverse section. 
Here the branch has a small pith. 
The specimen represented in Plate 17, fig. 8, is interesting, for it proves very clearly 
that the branch rootlet is an endogenous appendage of the parent axis. In this case 
neither has any pith. 
In Plate 15, photograph 7, we have illustrated a specimen which appears to deviate 
from the normal mode of branching. The main root, in its decorticated condition, is 
about 8 millims. in maximum diameter. It has a large pith, and no less than sixteen 
groups of primary xylem. The secondary wood is from fifteen to thirty elements in 
radial thickness. A branch, which is shown in nearly median section, lies exactly 
opposite one of the protoxylem-strands, but is separated from it by about fifteen 
layers of secondary wood. The inner extremity of the branch, in which both 
medulla and primary xylem are evident, ends quite sharply, and there is no 
* Winuiauson, “ Organization,” Part IX., Plate 19, figs. 2 and 4; Part XII., Plate 29, fig. 7. 
+ As in “ Organization,” Part IX., Plate 19, figs. 2 and 4. 
t So also in “ Organization,” Part XIL., Plate 29, fig. 7. Itseems that in this curious specimen the 
relatively main axis is that marked a’, which is seen in longitudinal section. 
§ C.N. 1321 (not figured). 
