ORGANIZATION OF THE FOSSIL PLANTS OF THE COAL-MEASURES. 741 
pointed out the remarkable combination of fern-like and Cycadean characters pre- 
sented by the stem and foliage of the plant. We now see that its roots show still 
more striking peculiarities. With a primary structure like that of the roots of 
Marattiaceze they combine a mode of secondary growth which recalls that of a typical 
Dicotyledon, a resemblance which, we need hardly say, is not indicative of affinity. 
D.—Hasit anp Dimensions oF THE PLANT. 
The specimens of Lyginodendron, on which the preceding description has been 
based, are all of comparatively small size, the maximum diameter of the stem not 
exceeding about 4 centims, 
It has been supposed that the plant attained arborescent dimensions, The evidence 
from this belief is derived partly from certain cortical impressions of large size, partly 
from a single large specimen, with the structure of the secondary wood preserved, 
the real nature of which, however, is not certain. 
Four examples of the cortical impressions in question were figured in Memoir IV., 
Plate 27. They obviously represent the casts of a “ Dictyoxylon” cortex of a very 
large stem. The furrows, no doubt, correspond to the print of the sclerenchymatous 
network, the elevations to the soft parenchyma by which the meshes were filled. 
A general resemblance to the outer cortex of Lyginodendron is obvious; but this 
seems to be the only reason for connecting these impressions with our plant. The 
meshes of the cast are of very large size, reaching a length of as much as 8 centims. 
We have received, through the kindness of Mr. A. C. Szwarp, F.G.S., a photograph 
of a still finer specimen of this kind from the “Third Grits” in the neighbourhood 
of Harrogate. This impression is almost a metre (38 inches) long and 28 centims, 
(114 inches) in maximum width, The meshes of the cast are long and pointed in form 
and very variable in size, reaching a length of at least 14 centims. Some of the 
larger meshes are sub-divided by oblique furrows, which no doubt represent the 
prints of subsidiary connecting strands of sclerenchyma. The specimen seems to be 
nearly flat, so that it is impossible to form any definite idea of the size of the stem to 
which it belonged, but it must certainly have been a good-sized tree. 
We do not think, at present, that there is any sufficient proof that these iarge 
cortical impressions belong to Lyginodendron. We have no undoubted Lyginodendron 
in which the meshes of the outer cortex at all approach the dimensions of those in 
the casts. The length of the meshes in Lyginodendron rarely exceeds 6 millims. 
_ It seems quite possible that the large casts may represent the outer bark of some 
species of Sigillaria, in which case their dimensions would present no difficulty. We 
know that the outer secondary cortex of Sigillaria possessed “ Dictyoxylon” 
structure,* as is well shown in sections of Sigillaria spinulosa from M. Renactt’s 
* See Sonms-Lausacs, “ Fossil Botany,” p. 247, &e. 
