494 
Watson. — On the Structure and 
The other type of oval scar, with a central umbilicus, can only be 
produced when the outer surface of the scar was, in life, nearly flat ; this 
is readily obvious from the inspection of hypothetical median longitudinal 
sections. 
It thus appears that ulodendroid scars may be flat or nearly so. 
It is almost certain that the scars of Ulodendron proper, that is, the type 
with contiguous circular scars and a central umbilicus, were also usually 
flat, or at most only slightly depressed. 
The proof of this statement is as follows : 
1. There is in the Manchester Museum a portion of a round stem of 
Ulodendron preserved in ironstone, which is apparently uncrushed, and in 
which the scars are essentially flat. 
2. If the scar had been at all deeply conical, the tissue composing it 
would have been puckered when it was crushed flat. Such well-preserved 
external surfaces as the originals of PL XXXVIII, Figs, i and 2, never show 
any sign of such puckering. 
At the same time, a well-preserved specimen from Low Moor, in the 
Bradford Museum, which is preserved in ironstone, and hence only slightly 
crushed, does show slightly depressed areas. The only specimen which has 
ever been figured as showing the scars as deep conical pits is that described 
by Carruthers. 1 This specimen, which I have never seen, has probably 
been misinterpreted. It is possible that it was so preserved that the leaf- 
trace bundles going to the scar were interpreted as the scar surface itself ; 
at any rate it seems certain that, in the vast majority of cases, the scars of 
Ulodendron , sensu striciu, were flat, or at most but slightly depressed. 
The question of the attribution of ulodendroid trunks to different 
genera presents some difficulties. 
It is generally conceded by all palaeobotanists that those specimens 
with oval, well-separated scars and an eccentric umbilicus belong to 
Bothrodendron . 
Those specimens which have the scars oval, well separated, and with 
a central umbilicus, occur in the Lower Carboniferous as well as in the Coal 
Measures, where they appear to be very rare. 
In all cases that I have seen, or found recorded in the literature, 
individuals of this type have their leaf-bases higher than they are broad, 
and apparently of the Lepidodendron type. Those from the Lower 
Carboniferous of Scotland were referred by Dr. Kidston in 1885 to Lepido- 
dendron veltheimianum ; the very few Coal Measure specimens I have seen 
are referable to Kidston’s L. Landsburgii. 
These specimens have leaf cushions often well preserved, and strikingly 
like those of Lepidodendron ; but in those cases that I have seen the leaf-scar 
is never visible, and the leaves seem to have remained attached to the stem 
1 Monthly Microscopical Journal, vol. iii. 1870, p. 144. 
