OF THE BRITISH COAL MEASURES. 85 
cut a little distance above the University College section, the outer trace has 
disappeared, having no doubt passed out into the petiole. The double trace 
shown (l. e. pl. 28. fig. 30, lt.) in the disorganized pericycle corresponds in 
position * to that which in the former section was still in connection with the 
wood. At the level shown, the two bundles have not yet begun to divide 
into four. No other trace is present in the Williamson section. 
The other transverse sections afford no new data, but the Williamson 
longitudinal section (W. 1304 B) is of considerable importance, as it shows a 
leaf-base in connection with the stem, a point not noticed at the time of the 
previous deseription. The preservation of the leaf-base is not very good, but 
the main features of the structure are clear. The petiole is attached obliquely 
to the stem, which it appears to exceed in width; the cortical tissues are 
perfectly continuous throughout. A layer of sclerenchyma, seen in tangential 
section, forms a partial barrier between stem and leaf-base. The latter has 
a Sparganum hypoderma and sclerotic masses like those of the stem. The 
important point is that it contains two double bundles or bundle-pairs. They 
are widely separated, but in each pair the division into two has only gone 
about as far as in the transverse section figured (Pl. 2. Phot. 14). It appears 
then, that the leaf-trace passed into the base of the leaf as two bundle-pairs, 
and not as four independent bundles, thus resembling H. tiliwoides rather 
than H. shorense. 
The “eylindricum” specimen thus throws a good deal of light on the 
course of the leaf-traces. It does not differ in any essential respect from the 
other examples of Æ. Lomawii described, though it does not exactly agree 
with any of them; the trace-bundles are fairly large, but do not separate 
very widely from eaeh other in passing through the stem; this is probably 
because in this case no roots arose between the strands. The leaves were at 
somewhat long intervals, for in most of the transverse sections only one trace 
is met with. The * eylindricum" stem is evidently a specimen of the rather 
variable Dulesgate species, /7. Loma«ii. 
H. Lomazii, Form a. 
This form was shortly described and admirably illustrated by Williamson 
in his 17th Memoir (1890, p. 96, pls. 14, 15. figs. 14-18). — A section of it 
was also figured in our joint paper (Williamson & Scott, 1895, p. 753, pl. 26. 
fig. 21) and shows a branch in connection with the stem ; I believe this is 
still the only recorded case of branching in the genus Zeterangium. 
The specimens are all more or less crushed, and present a rather singular 
appearance, different from that of most Heterangiums. This is chiefly due 
to the faet that the cortex, owing to the great development of the sclerotic 
* As the two slides are reversed, it is impossible to figure them with corresponding 
orientation. 
