ORGANIZATION OF THE FOSSIL PLANTS OF THE COAL-MEASURES. 761 
These masses were separated from one another by the broad principal rays, which 
were continuous towards the interior with the bands of conjunctive tissue lying 
between the primary xylem-strands. There was no inter-fascicular formation of 
either wood or bast, and consequently the definite distribution of the secondary 
tissues gives a very characteristic appearance to the transverse sections. 
Both primary and secondary tracheides are nearly though not exactly similar to 
those of H. Grievii ; the spivally-arranged bordered pits have narrow inclined slit- 
like openings.* 
The secondary tracheides, in addition to the crowded bordered pits on their radial 
walls, had more scattered, sometimes simple, pits on their tangential faces. 
Many of the secondary rays by which the wood is divided up extend inwards as 
far us the primary xylem. 
In many places the cambium is extremely well-preserved (see Plate 29, figs. 35, 36, 
and 37). The fascicular cambium is of the usual character, but here, as in Lygino- 
dendron, the cambium by which the principal rays were formed shows less frequent 
tangential divisions. . 
In the radial section represented in fig. 37, a tracheide (tr.) adjoining the cambium 
is shown, the wall of which is areolated, though not yet pitted in the usual manner. 
This is evidently a tracheide in course of development; the primordial pits are 
already marked out, but the deposition of the borders has not yet begun. This is 
not an isolated case. We have observed in the same material a tracheide, with a 
still finer areolation, representing a still earlier stage, and another somewhat more 
advanced, with the borders of the pits beginning to appear. Such stages of histo- 
logical development are certainly rarities among fossil specimens. 
The enormous masses of phloém constitute the most interesting feature of the fossil. 
The phloém attains a thickness little less than that of the secondary wood, and is 
preserved in marvellous perfection. 
The primary rays in passing through the phloém become greatly dilated, widening 
out into large wedges, ‘as seen. in transverse section, and thus exactly resembling the 
well-known phloém-rays of the lime tree, a resemblance to which the fossil owes its 
specific name.t 
At the exterior of each phloém-strand the irregularly arranged, somewhat thick- 
walled elements of the primary phloém can be easily recognized (fig. 35, ph.). The 
greater part of the bast, however, is secondary, as shown both by its radial seriation 
corresponding with that of the cambium and wood, and by the proportion which its: 
thickness always bears to that of the secondary wood. 
The secondary rays of the phloém are often dilated in the same way as the primary 
rays, but to a less extent. The phloém groups lying between the rays show no very 
obvious differentiation of their elements as seen in transverse section (figs. 35 and 36). 
* See Wittiamson, Part XIII, Plate 21, fig. 16. 
+ See Wittiamson, Part XIII., Plate 21, figs. 1, 4, and 10; Plate 22, fig. 2; Plate 23, fig. 9. 
MDCCCXCV.-——B. 5 F 
