i54 Lady Isabel Browne. 
and the presence of a ligule. But as the Lepidodendraceae are the 
only well-known dendroid Lycopods, and as they were certainly a 
dominant group in the middle Coal Measures, from which Pinako- 
dendron comes, it seems probable that the latter belongs to this 
cycle of affinity. 
The comparatively simple anatomy of the stem of the 
Lepidodendraceae points them out, in spite of their great size, as 
a relatively primitive order, and the high specialization of their 
underground organs, the Stigmariae, seems to preclude the idea of 
their having undergone any considerable reduction. For these 
reasons and on account of the want of differentiation between its 
leaves and sporophylls it seems preferable, pending the publication 
of Mr. Kidston’s paper, to regard the non-strobiloid condition of 
Pinakodendron as primitive. But in by far the greater number of 
cases the fructifications were cones; sometimes these were 
undoubtedly borne at the ends of slender branches. Until quite 
recently it was held that they were sometimes also borne on the 
old stems ; such forms were known as Ulodendron. Their stems 
bore the ordinary Lepidodendraceous markings—either of the 
Lepidodendron or of the Sigillaria type, but they also bore large 
roundish scars, usually disposed in two longitudinal rows; some¬ 
times these scars appear to have been arranged quincuncially 
(14). They are slightly depressed structures, at the bottom of 
which is a small circular scar known as the umbilicus; the 
umbilicus is slightly excentric, being nearer the lower edge of the 
main scar, and from it slight ridges radiate upwards and outwards; 
the lower part of the scar bears spirally arranged dots. These 
Ulodendroid scars are usually interpreted as being the marks left 
by very big deciduous sessile cones, the umbilicus representing the 
very short peduncle, and the radiate markings being due to the 
pressure on the growing stems of the base of the large cone. Mr. 
Watson, however, has shown that this explanation is inadequate ; 
he points out that these scars occur on the stem of Bothrodendron 
mundum, and that there is a very strong probability that the cones 
of this species were small structures borne on comparatively 
slender twigs (25). Unfortunately the connection between these 
cones described by Mr. Watson and Bothrodendron mundum is not 
absolutely proved, though it is very strongly supported by the 
constant association of the two structures and the close similarity 
of the wood in the axis of the cone to that of a small twig of 
Bothrodendron mundum (24). Mr. Watson maintains that the 
