or THE FOSSIL PLANTS OF THE COAL-MEASURES. 
211 
1 
Plate. 
Fig. 
Ppges on wliicli 
references are 
made to the 
figures. 
6 
9 
The vascular bundle of another stem, now converted 
into a vasculo-medullary cylinder, 6, //, enclosing a 
small but distinct medulla, a, consisting of very 
few cells. Cabinet number, 406. X 90 ... . 
197, 205 
6 
10 
Another stem, in which the medulla, a, is larger and the 
medullary cells more numerous and thin-walled, as if 
recently sub-dividecl. Cabinet number 416c . 
197, 205 
6 
11 
Transverse section of another stem, in which the 
medulla, a, has enlarged yet further and its component 
cells have assumed their matured parenchymatous 
form. Cabinet number, 405. X 90 . 
197, 205 
6 
12 
Transverse section of my largest stem of this 'Hiundum 
type, showing an enormous increase alike in the 
number of the vessels of the medullary vascular 
cylinder, h, ?/, and of the cells of the medulla, a. 
Cabinet number, 413. X 66. 
197, 205 
6 
13 
Longitudinal section through the central j)ortion of a 
stem, showing the medullary cells at a, the medul¬ 
lary vascular cylinder at h, and the cells of the 
innermost cortex at c, c. Procambial (?) cells at c . 
Cabinet number, 414. X66. 
197 
6 
14 
Transverse section through another stem, in which the 
medullary-vascular axis, a, h, is dichotomising in 
the usual Lepidodendroid manner. Cabinet number, 
412.' X 66. 
198 
5 
14a 
Small portion of a scalariform tracheid of the medullary 
' vascular cylinder of L. mundiim, fig. 13, h, showing 
three of the bordered pits traversed vertically by very 
delicate lignified threads. X 650 . 
197 
5 
14b 
Portion of a single bordered pit of 14 a, magnified 
1,800 chameters : a, a, the transverse lignihed bars ; 
b, the vertical threads. 
197 
5 
15 
Part of a transverse section in which the medullary 
vascular cylinder, h, is invested by a relatively thick 
exogenous zone, d. Cabinet number, 4166. X 65 . 
198 
i 
2 E 2 
