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Explan ATION OF PLATE 56. 91

coast of Northumberland. This fragment is about five feet high, and two feet three inches in diameter at its base.” Scale one-twenty-fourth. (Sopwith.) 2. Fragment of the bark on the trunk of a Sigillaria, from Earl Fitzwilliam's coal-mine at Elsikar, near Rotherham. In this mine many large trunks are seen inclined in all directions, and some nearly vertical. (See W. I. p. 353, Note.) The bark is converted into a thin lamina of coal, and remains attached to the lower portion of this specimen. It exhibits on its outer surface scars formed by the articulations of the bases of leaves; these are penetrated near their centre by three apertures for vessels that passed from each leaf into the trunk. The decorticated upper part of this specimen presents an impression of its striated internal surface, and exhibits beneath each scale two oblong parallel apertures, through which the vessels from a leaf penetrated the trunk. Scale one-half. (Original.) The substance of the trunk must have been in a state of decay, before the mud, which is now hardened into shale, could have entered the interior of the bark. When trunks of this kind are inclined at an angle exceeding 45°, they are usually distended with sandstone, or sandy shale; when at a less angle than 45°, they are most commonly compressed, and have only a thin flat portion of shale, formed of indurated mud within their bark. The bark, wherever it has not perished, is converted to coal. 2'. Articulating leaf-scar on the exterior of the bark of another large trunk of Sigillaria from Elsecar. Nat.

* M. Ad. Brongniart found a stem of Sigillaria in a coal-mine at Essen in Westphalia, which was dichotomous near its top.

Fig.

size. On comparing this scar with those upon the
bark of Fig. 2, it may be seen that the different
modes of articulation of the leaves with the cortical
integument present obvious characters, on which
specific distinctions may perhaps most easily be es-
tablished, in this very obscure and curious family of
extinct plants. See various figures of these leaf-
scars in Lindley and Hutton's Fossil Flora, Plates
55.56. 57. 71. 72. &c. In Figs. 2, and 2', as in
many other species, decurrent lines are visible on
both sides of the scar. (Original.)
3. Ulodendron Allanii, (nobis) scale one-fifth. See
V. I. p. 356. Note. Drawn from a plaster cast of an
impression on sandstone, in the Museum of the Royal
Society of Edinburgh from the Coal formation at
Cragleith. This sandstone has formed a natural
mould on the outer surface of a stem, which has
entirely perished; our cast gives a fac-simile of the
small rhomboidal scales, and of three large round
scars on the exterior of the trunk. This impression
has been figured, in an inverted position, by Mr.
Allan in Vol. IX. Trans. Royal Soc. Edin. 1823. Pl.
XIV. p. 236. (Original.)

Our figure represents the trunk in its natural position. In the centre of each scar is a cavity, indicating the place of attachment of a cone. The upper portion of each scar is marked with furrows, produced by pressure of the long radiating scales at the bottom of the cone. This pressure has nearly obliterated the smaller rhomboidal scales of the bark, in those parts where the furrows are deepest; on the lower portion of the scars, the scales of the bark have been but slightly modified by pressure of the cone.

Fig.

Fig.

ExPLANATION OF PLATE 56. 93

4. A single scar formed by the attachment of a cone
of another species, Ulodendron Lucasii, (nobis,) dis-
covered by Mr. Lucas in the S. Wales Coal field
near Swansea. Some scales and speared-shaped
leaves of the trunk are still preserved around the mar-
gin of this scar. As the bark has fallen off, we have
only the impression of its inner surface. This sur-
face exhibits small apertures, through which vessels
entered from beneath the bark-scales into the trunk.
On the upper part of the disk, the traces of many of
these vessels have been obliterated by pressure of the
cone. Scale one-fourth. (Original.)
5. Ulodendron Stokesii. (nobis.) A large oval scar,
4} inches in its longer, and 3} inches in its shorter
diameter) preserved in shale from an unknown lo-
cality in the English Coal Formation. On the
margin of this scar are the remains of rhomboidal
scales, and impressions of scales, and a few small
leaves. Within the disk a few fragments only of
the bark remain near its upper margin. Near its
centre, is the mark of the insertion of the stem of
a large cone. The lower half exhibits a series of
small tubular cavities, marking the place of vessels
which passed from the bark into the trunk, one
beneath each of the bark-scales that have fallen off.
In the upper half of the Scar, there are but slight
traces of these cavities, and the surface is marked
with furrows, produced by pressure of the long
radiating scales of the base of the cone. Scale
one-fifth. (Original.)

. 6. Ulodendron Rhodii. (nobis.) Scar on a scaly

stem, from the Coal field of Silesia, figured by Rhode in his Beitrage zur Pflanzemkunde der Vorwelt, L. 2. Pl. 3. Fig. 1. The lower portion of this Scar Fig.

retains the bark-scales modified by pressure of the
Strobilus or cone that grew from the centre of the
disk. The upper portion of the Scar is without in-
dications of bark-scales, and is covered with radiat-
ing furrows, in pressed on it by the long slender
scales of the base of the Strobilus, which have obli-
terated the bark-scales.”
The character of this scar approaches to that of
Fig. 5, but its proportions differ, measuring 3} inches
in the longer, and 2% inches in the shorter diameter.
The scaly bark (which in Fig 5 has been almost en-
tirely removed from the area of the scar) is pre-
served on the lower portion of the disk of Fig. 6.
Scale two-ninths. (Original.)
6'. Cast of Ulodendron Conybearii (nobis) formed by
Pennant sandstone of the Coal formation at Staple-
ton near Bristol. This cast expresses the exact form
of an oval scar, or cavity on a stem from which a
cone had fallen off.
The disk is covered with slight ridges and furrows,
radiating in all directions from the point of insertion
of the cone, and formed by pressure of its lowest
scales upon the portion of the stem to which it was
attached. Beneath the point of insertion, a few small

*The portions above and below the line drawn across Fig. 6, are copied from two scars in Rhode's figure. Rhode considers these impressions to be flowers, and the compressed bark-scales to be the Petioles of the flower, and has represented the trunk in an inverted

position.

As, in every species of Ulodendron which we have seen, the furrows produced by scales at the base of the cone, are deepest on the upper portion of the Scar, we infer from this circumstance that the cones were inclined upwards and inwards, with their axis approximating to that of the stem from which they issued.

Fig.

Fig.

EXPLANATION OF PLATE 56. 95

scales of the bark remain adhering to the Sandstone.
Scale one-fourth. (Original.)
7. Portion of the Trunk of Favularia, one-fourth nat.
size. This plant is distinguished by the tessellated
appearance of the scales, which cover the space be-
tween each fluting of the Bark. In the centre of the
area of each scale is a club-shaped scar, which gave
origin to a leaf; it was a dicotyledonous plant, pro-
bably allied to Sigillaria; and its stem must have
been covered with a mass of densely imbricated fo-
liage. In the Genus Sigillaria the leaves were more
distant from one another. The Rows of scars are
separated by a groove, Fig. 7. b.; their disposition
in the vertical direction is indicated by the line a.
(Lindley, Foss. Fl. Pl. 73.)
8. Reduced from Lindley and Hutton's figure (Pl.
31) of the central portion of a Stigmaria ficoides,
from Shale in the roof of the Jarrow colliery near
Newcastle. We have here a view of the inferior
surface of this curious plant. Its dome-shaped
hollow central trunk, or stem, was three feet in
diameter, and fitted to sustain horizontally in a
floating position the numerous long branches by
which it was surrounded; these divide into two, at
a certain distance from the Trunk. When perfect,
and floating in water, its appearance must have
resembled the form of an Asterias. On the two
longest branches, a b. is seen the longitudinal de-
pression, which is usually adjacent to the small
internal woody axis of these branches, and from its
position in this fossil, we learn that the place of
this depression was on the inferior surface of each
branch. Scale one-twenty-fourth. (See W. I. p.
358.)

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