56 
PROFESSOR W. C. WILLIAMSON ON THE ORGANIZATION 
what rigid manner, projecting considerably beyond the verticils of sporangia. The 
sporangia, as seen in a fractured fragment not yet cut up into sections, are obtusely 
angular, especially at their inner sides, the result of the mutual compression of con- 
centric circles of rounded spheres. They were attached to the bractigerous disks by 
numerous long, slender, cylindrical sporangiophores, v. Since writing my original 
memoir, I have ascertained that these sprang from each margin of the base of each 
bract so as to constitute two parallel series. This relation of the sporangiophores to 
the bracts from which they spring is well seen at t', where the bases of the pairs of 
sporangiophores appear to project inwards (though they are really proceeding upwards 
and outwards) from each subdivision of the nodal disk. I have already pointed out 
that each bract obviously had one thick midrib especially conspicuous near its base. 
In my memoir, speaking of the spores, I stated that “ at the first glance we should be 
tempted to infer that their exteriors had been spinous ; but I have not been able to 
satisfy myself that such has been the case ” (loc. cit. p. 34). But since the above 
sentence was penned I have obtained yet finer examples of these spores, some of which are 
represented in Plate V. fig. 30, affording proof that long spines projected from their outer 
surfaces, the bases of these spines being connected by a coarse network of thickened 
ridges, reminding us of the aspect of the macrospores of Selaginella incequifolia and 
other Lycopodiaceous fruits. The size of my newly discovered spores, including the 
length of the spines, is about '0044. In my memoir I stated that it was '0037 ; but the 
small discrepancy is accounted for by the fact that in the latter the spines were imper- 
fectly preserved, hence their remarkable length was not known, and consequently not 
included in the measurement*. 
I think that the preceding description must satisfy the most incredulous that 
this fruit belongs to the same plants as the stems described in the earlier part 
of the present memoir f. The two agree exactly in the form and composition of 
the central, non-exogenous, vascular axis, in possessing a bark of which the inner 
portion was composed of delicate cells whilst the outer one consisted of coarse 
parenchyma, and in the expansion of the latter at each node into a prosenchymatous 
leaf-bearing disk. The identity of the triangular axis forming the centre around 
which the exogenous growths were developed in the stems of Aster ophyllites with 
the entire axis in the fruit is precisely what we should expect. I have pointed out, 
in my previous memoir on the Burntisland Lepidodendra , that the structure of the 
vascular bundle or bundles of a strobilus, which is usually a deciduous annual 
growth, is, as might have been anticipated, almost identical with that of the 
corresponding twigs developed upon the branches within the same limited period. 
* These spores appear to me to bear a resemblance to the objects from the Coal-measures described by Mr. Car- 
RtriEERs as radiolarian rhizopods, and to which he has given the generic name of Traquairia. See the Report of 
the British Association for the Advancement of Science for 1872 (Trans, of Sect. p. 126). — February 9, 1874. 
t I conclude that the fruit belongs to Asteropliyllites rather than to Sphenophyllum, from the circumstance 
that its nodal disks subdivide into numerous narrow bracts instead of into a small number of broader ones. 
