OF THE FOSSIL PLANTS OF THE COAL-MEASURES. 
533 
our sections of Lepidostrobi . The detached masses of prosenchyma, c, c, are portions 
of the outermost cortical layer of the axis of the strobilus, which are being prolonged 
radially into the usual Lepidostroboid sporangiferous bracts. Extensions of these 
bracts radiate, in a more or less fragmentary form, to the circumference of the specimen, 
which even in its imperfect state indicates a cone having a diameter of fully an inch. 
Interspersed amongst these bracts or sporangiophores are the usual sporangia, the wall 
of each of which displays the structure so common amongst these carboniferous Crypto¬ 
gams, viz.a single series of cells elongated vertically to the surface of the sporangium, 
and having their two extremities flattened, so that the two surfaces of the sporangium 
wall exhibit the ordinary aspect of tubular thick-walled parenchyma (fig. S3), whilst 
vertical sections present the aspect seen in fig. 84 or that of cylindrical parenchyma. 
One of these sporangia is shown in fig. 85, a, enlarged 16 diameters, and contains 
three of the Traquarian macrospores. At ct are fragments of two other contiguous 
sporangia. Throughout the greater part of its extent the sporangium wall, a, exhibits 
the appearance of fig. 8 4, but here and there its flexures have caused it to be intersected 
obliquely, as at a", where it resembles fig. 83. Two of the macrospores are intersected 
nearly through their centres, the third one more tangentially, hence its apparent smaller 
size. The specimen from which this and other similar sections were prepared not only 
places the vegetable nature of these Traquarice beyond the possibility of doubt, as 
well as demonstrates the fact that they are Lycopodiaceous in character, but from the 
excellent preservation of the macrospores, throws further light upon their structure. 
That the specimens with tuberculated but unbranclied spines (represented by figs. 
40, 41, and 42, of the earlier portion of this memoir) are immature, whilst those repre¬ 
sented by figs. 45 and 46 are more matured examples, is now clear. I think there is 
no doubt but that in the young state there was a distinct outer exosporium and an 
inner endosporium. At an early period the exosporium became differentiated into 
two layers. Of these, the inner one (represented by /’in fig. 42) retained its structure¬ 
less, spherical form, being undistinguish able from the endosporium, fig. 42 f', in all 
points save in its more external position. The outer layer of this exosporium, fig. 42, a, 
on the other hand, underwent a development into a system of ramifying tubes, the com¬ 
plexness of which exceeds what I had observed to be sufficiently remarkable when the 
earlier part of this memoir was written. There is now no doubt that the minute pro¬ 
jections, a, from the radiating spines of fig. 44 with the delicate branching threads 
which spring from those projections, are the early conditions of the branching tubes 
seen in fig. 50. The almost invisible threads expand into a series of tubular dichoto¬ 
mous branches. 
Fig. 86 represents a portion of a tangential section of one of the macrospores from 
Mr. Cash’s strobilus. At a we find what I assume to be the inner structureless 
layer of the differentiated exosporium, now very distinctly separated from its outer 
tubulated one ; b, d represent the transversely intersected bases of 11 of the branch¬ 
ing tubes, a, b, of the figs. 40-49 of the memoir. We now see that in addition to 
MDCCCLXXX. 3 Z 
