ORGANIZATION OF THE FOSSIL PLANTS OF THE COAL-MEASURES. 753 
in the outer layers of the pericycle,* yet the formation of a regular periderm does not 
seem to have been general in this species. 
5. The Cortex. 
_ The wide inner cortex consisted of short-celled parenchyma, interrupted by very 
regular horizontal plates of sclerotic tissue (see Plate 26, figs, 21 and 22+), These 
sclerotic plates give a most characteristic appearance to the sections both of stems 
and petioles. They appear to have been of the same nature as the “sclerotic nests,” 
which are so general in Lyginodendron, but their distribution is different. In 
Lyginodendron they occurred mainly in the pith and pericycle of the stem and in the 
cortex of the petioles. In HH. Giriew they are always cortical in both organs. Their 
sclerotic character is more easily recognized in the latter plant, where their 
walls are often prefectly preserved. In some cases, even the numerous fine pits 
running through the whole thickness of the cell-wall can be distinguished.{ These 
elements bear a considerable resemblance to the stone-cells, which are so often found 
in the cortical tissues or petioles of recent plants, as, for'example, in Hoya, 
The sclerotic plates were evidently placed one above the other in vertical series, 
for a radial section either shows a whole row of them or else misses them altogether.§ 
The arrangement of their constituent cells is very regular and indicates that they 
were formed by a special meristem. | 
The outer cortex consisted of the well-known alternating strands of sclerenchy- 
matous fibres and parenchyma. The parenchymatous portions are often very narrow, 
especially in the Dulesgate specimens, in which the sclerenchyma appears nearly 
continuous and is only interrupted here aud there by small patches of parenchymal 
(see fig. 21). 
The epidermis is sometimes preserved and consisted of rather thick-walled cells. 
In one case we noticed an appearance suggestive of ¢ a depressed stoma, lying over one 
of the parenchymatous groups of the outer cortex,** 
6. Branching of the Stem. 
We have only a single specimen in which the branching of the stem is shown. 
This is one of those from Dulesgate, A. transverse section of this specimen is shown 
* G.N. 1276. 
+ Also Wittramson, “ Organization,” Part IV., Plate 29, fig. 32, h’, and Part XVIL., Plate 15, figs. 17 
and 18. 
t See C.N. 1915 F. 
§ C.N. 1276. 
|| Wittramson, “ Organization,” Part XVII. Plate 15, figs. 17 and 18. 
4{ Wittramson, “ Organization,” Part XVII, Plate 14, fig. 14. 
** C.N. 1915 M. 
MDCCCXCV.—B, 5 E 
