OF THE BRITISH COAL MEASURES. 73 
The pericycle is very wide, 820 u to 900 u, in the young specimen 4 
(Phot. 7), and 1:1 to 2'2 mm. in the more mature specimen 2 (Phot. 3). 
The cells are very frequently found in a state of division, especially in the 
inner layers, so no doubt this zone grew with the growth of the stem. The 
pericyclic selereides are chiefly found in the inner portion ; their extent 
varies much in the different specimens. 
The fact that the pericycle is usually better preserved than the cortex 
(almost wholly lost, for example, in specimen 4, otherwise so perfectly 
preserved) might be thought to indicate some structural peculiarity. But 
specimen 1, as we have seen, is an exception, and, where the cortex is found; 
it has the typical Heterangium structure, with plates of sclereides in the 
ground-tissue and a “ Sparganum ? hypoderma, but not very strongly 
developed. 
The course of the leaf-traces has already been dealt with; while, differing 
conspicuously from the monodesmie type represented by the Lower Car- 
boniferous M. Grievii, it agrees essentially with that of other Coal-Measure 
forms. The rapidity with which the leaf-traces were given off varies with 
different specimens. Thus, in specimen 3 there are never more than two 
traces shown in the transverse section, while in specimen 1 there are as many 
as four, if we include the leaf-base attached to the stem. It may be worth 
noting that in /7. tilivoides the two strands of the trace, where they leave the 
stelar wood, are near together, though distinet; in some other Coal-Measure 
forms they are much wider apart to start with ; this, however, affords no 
certain specific distinction. 
It is not perfectly certain that the stem described as H. shorense may not 
be a young specimen of H. tiliwoides, but there are several small distinctions, 
such as the more regular grouping of the metaxylem tracheides in H. shorense, 
the apparently narrower pericycle with sclereides at the periphery, and the 
division of the leaf-trace into eight in the petiole. As the localities are 
different, H. tilivoides coming from the Halifax Beds and H. shorense from 
Dulesgate, there is no presumption that they are identical, and it is better to 
keep the two distinct. The following diagnosis may be given :— 
Fleterangium tiliwoides, Will. 
Stem from about 10 mm. to about 16 mm. in diameter. 
Primary wood arranged in more or less definite packets, separated by 
parenchyma. 
Tracheides often with a spiral band between the pits. 
Secondary phloem much developed, often equalling or exceeding the 
secondary wood in thickness. Phloem-rays much dilated. 
Peripheral xylem-strands and leaf-trace bundles mesarch, with little 
centrifugal wood. — , 
Pericycle broad. Sclerotic tissue present both in perieyele and cortex. 
LINN. JOURN.—BOTANY, VOL. XLIV. G 
pt A 
