78 DR. D. H. SCOTT ON THE HETERANGIUMS 
Sclerotic groups are frequent in the perieycle: in most stems they are 
quite conspicuous ; in specimens 5 and 6 they are not so easy to find, but 
this seems to be only because their cell-walls are less thickened. The 
sclereides are short elements, but (to judge from the longitudinal section 
R. 638) appear to form vertical strands of considerable length. The pericyclic 
parenchyma consists of short cells, many of which have the dark contents 
above referred to. 
On the outer border of the perieyele tangential divisions have sometimes 
taken place, giving rise to a tissue resembling an internal periderm, such as 
we find in Lyginopteris *. This is best shown in specimen 1 (e. g., S. 447). 
The cortex is well preserved in certain cases, though often the parenchy- 
matous part of the inner zone has perished, with the result that the 
Sparganum hypoderma is sometimes stripped off. When the parenchyma is 
preserved it consists of large, short, thin-walled cells. Here, as in other 
species, the sclerotic plates of the inner cortex are a conspicuous feature. 
Their transverse diameter may be as much as 1°4 mm. In the descriptions 
previously given they are confused with the corresponding structures in the 
true H. Grievii t ; in reality those of H. Lomazii are quite distinct. They 
here form massive blocks, rather than plates, reaching a thickness of about 
15 cells and 0*6 mm. In the middle part the cells are flat and thick-walled, 
while towards the upper and lower edges they become longer, with thinner 
walls. All the cells are regularly ranged in vertical rows (see Pl. 4. fig. 15). 
Corresponding to their bulky form, the sclerotic masses are rather widely 
spaced. In H. Grievii the plates are much thinner and seldom more than 
four cells or about 0'2 mm. in thickness ; they are also more numerous. The 
contrast is striking if one compares fig. 15 in this paper with Williamson’s 
figure of H. Grievii (Williamson, 1873, pl. 29. fig. 32). H. tiliwoides is 
intermediate in these respects (Williamson, 1887, pl. 22. fig. 11). As regards 
the sclereides themselves, the apparent thickness of their cell-walls varies 
much. In some cases it is probable that the walls were not really as thin 
as they appear, the thickening layers originally present having become altered 
and obscured. 
The parenchyma of the inner cortex consists of rather large, short or 
slightly elongated, thin-walled cells. The Sparganum hypoderma 1, or outer 
cortex, varies a good deal in the different specimens. As a rule, we find the 
usual alternating radial bands of sclerenchyma and parenchyma ; the former 
are commonly broad and not much elongated radially, and thus quite 
different from those of H. Grievit §. The bands sometimes anastomose. In 
* Williamson & Scott, 1895, p. 718, pl. 21. fig. 1; pl. 22. figs. 5-7. 
T Asin Williamson & Scott, l. c. p. 753. 
t The name“hypoderma,” though commonly used, is not strictly correct, for the Sparganum 
zone does not border immediately on the epidermis. 
$ Cf. Williamson, 1873, pl. 28. fig. 30; pl. 29. fig. 35. 
