ME. E. W. BINNEY ON SOME LOWEE-COAL-SEAM FOSSIL PLANTS. 
587 
vessels arranged without order, found in the inside of a stem of Sigillaria in such 
a position as it existed in the living plant. It is not a solitary instance, but one of 
more than fifty specimens exhibiting similar characters which have come under my 
observation. 
In Plate XXXII. fig. 1, is represented the light-coloured disk previously alluded to, 
and shown in Plate XXXI. of the natural size, but here magnified 5 diameters, exhi- 
biting the central axis composed of hexagonal vessels arranged without order, of several 
sizes, those in the middle being smaller and becoming larger towards the outside, where 
they come in contact with the internal radiating cylinder b , and then again diminishing 
in size. This latter was no doubt cylindrical, like the stem of the plant, but both parts 
in the process of petrification have been altered by pressure to their present forms. It 
consists of a broad cylinder ( b ) of about an inch in diameter, composed of parallel elon- 
gated tetragonal or hexagonal tubes of equal diameter throughout for the greater part 
of their length, obtuse and rounded at either extremity, and everywhere marked with 
crowded parallel lines which are free or anastomosing all over the surface. The tubes 
towards the axis are of the smallest diameter ; they gradually enlarge towards the circum- 
ference, where the largest are situated, though bundles of smaller tubes occasionally occur 
among the larger. This cylinder, which for convenience may be called the internal 
woody system of the plant, is divided into elongated wedge-shaped masses, pointed at 
their posterior or inner extremity, and parted by fine medullary rays of various breadths, 
some much narrower than the diameter of the tubes, others considerably broader, but 
none are conspicuous to the naked eye, except towards the outer circumference in some 
rare instances. 
Fig. 2 represents a transverse section of the central axis and the commencement of 
the internal radiating cylinder, magnified 12 diameters. The hexagonal vessels in the 
centre and at the circumference, where they come in contact with the internal radiating 
cylinder, are smaller in size than those seen in the other parts of the axis. The dark line 
across the axis, as well as the dark space in the centre, both seem to be the result of a 
disarrangement of the tubes during the process of mineralization, as similar appearances 
have not been observed in many other specimens examined by me, which in those parts 
are in a more perfect state of preservation. The dark and sharp line separating the 
vessels of the central axis from those of the internal radiating cylinder does not permit 
us to clearly see the origin of the medullary rays or bundles which undoubtedly traverse 
the latter. 
Fig. 3 represents a longitudinal section taken on the right-hand side of the specimen, 
and extending across the whole of the internal radiating cylinder through the central 
axis, the intermediate space between the internal radiating cylinder and the outer 
cylinder, and the external radiating cylinder to the outside of the stem, magnified 4 dia- 
meters : a a showing the smaller barred vessels of the central axis, having some ( a / a!) 
which appear to have been disarranged ; b b the internal radiating cylinder of larger 
barred vessels ; c the space occupied by lax cellular tissue traversed by bundles of vessels ; 
and d the external radiating cylinder, consisting of elongated tubes or utricles arranged 
mdccclxv. 5 L 
