489 
Origin of the Uloden droid Scar . 
vasculare may be a Bothrodendron , cannot be upheld, as the work of 
Hovelacque 1 has made us well acquainted with the characters of the leaf- 
cushions, which are typically lepidodendroid, and project considerably. 
It thus appears that the whole of the evidence that M. Renier has fur- 
nished in support of his theory is either incorrectly reported or readily 
explicable on the abscission layer theory of ulodendroid scars. 
Description of exceptionally Well-preserved Specimens of 
Ulodendron. 
I now propose to describe two exceptionally well-preserved specimens 
of Ulodendron which show that the leaf-traces seen in section on the outer 
surface of a ulodendroid scar have passed through the tissue of that scar 
and arisen within the trunk. The proof of this will show that M. Renier’s 
theory, on which the outer surface of the scar is the inner side of the outer 
cortex of the branch, and should of course receive its leaf-trace bundles 
from without, is incorrect. 
These two specimens belong to the Manchester Museum, and are 
examples of Ulodendron , sensu strictu ; they are preserved as flattened 
trunks in shale, and are remarkable because they show the outer face of 
ulodendroid scars as positives on a coal film. 
The finer specimen is a piece of trunk, which in its present flattened 
state measures 19 cm. across, and is 22 cm. long; in this distance it bears 
three and a half large ulodendroid scars. The whole of one side is still 
covered with a coal film, the surface of which is preserved with extraordinary 
perfection, being almost completely free from slickensides. 
The stem surface shows the longitudinal cracks which have been 
luminously explained by Kidston, 2 as being due to the rupture of the 
outer layers of the cortex, to accommodate the expanding stem. In 
the specimen under consideration, these cracks occur also on the scars, 
showing that considerable secondary growth took place after their 
formation. 
The best-preserved scar is represented by PL XXXVIII, Fig. 3. 
The general features are well shown in that figure, the sharply marked- 
off umbilicus, whose gently sloping edges show on the upper half small 
projections of the same size as the leaf-traces, which can only be the 
sections of leaf-traces cut during the almost vertical part of their passage, 
before they turn out into the middle cortex. The whole surface of the 
umbilicus is covered by a coal film, a fact which is against M. Renier s 
theory, because on his view it necessarily represents the phloem and middle 
cortex in addition to the wood of the branch, and these tissues would almost 
certainly have been defective. 
1 Mem. Soc. Linn, de Normandie, xvii. 
2 Ann. and Mag. Nat. Hist., ser. v, vol. xvi, pp. 123, 162, 239. 
