OF THE FOSSIL PLANTS OF THE COAL-MEASURES. 
525 
Radiolarians. Unfortunately, such a negative conclusion is more readily arrived at 
than a positive one, telling what these objects really were. They are wholly unlike 
any living organisms that we are acquainted with. Their spherical form suggests the 
possibility that they may have been the tests of some extinct form of Protozoa. The 
porous tissue seen in fig. 80 gives some support to the idea of their having been 
Foraminiferous—and the radiating structure seen in so many of the transverse sections 
is quite compatible with the same idea. On the other hand it is not impossible that 
they may have had some affinity with the recent Rhabdoliths and Coccoliths, though 
this does not seem very probable. The only other possibility that suggests itself is 
that they may be reproductive capsules of some marine form of vegetation, but no facts 
yet discovered afford any definite support to this hypothesis. Mr. Brady informs me 
that in one instance he found indications of spore-like objects in the spherical cavity, 
but the whole of the thousands which I have examined were entirely devoid of such 
elements. This fact is suggestive of their having been filled with some material 
incapable of fossilisation— e.g., of sarcodic protoplasm, pointing to a Protozoan nature. 
I have once more to acknowledge the assistance I have received from Mr. Spencer 
and Mr. Binns, of Halifax, from Mr. Earnshaw, of Oldham, and especially from Mr. 
Wunsch, of Glasgow, to whom we owe the discovery of the magnificent carboniferous 
forest of Laggan Bay, and whose invaluable aid demands my warmest thanks. Mr. 
Siddall, of Chester, has laid me under obligation for the Welsh limestones, and I am 
indebted to Mr. Henry Brady for calling my attention to the corniferous limestone of 
Kelly’s Island. 
Index to the Plates. 
PLATE 14. 
Lycopodiaceous Plants. 
Arran Lepidodendron. 
Fig. 1. Transverse section of one of the youngest twigs. a. Central vascular 
bundle, c. Leaves, c. Foliar vascular bundle. Enlarged 16 diameters. 
Fig. 2. Central vascular bundle of fig. 1. a. Small vessels at the periphery of the 
axis, from which the foliar vascular bundles ( b) arise. Enlarged 37 
diameters. 
Fig. 3. Transverse section of a larger branch, a. Central vascular bundle expanded 
into a medullary cylinder, b. Foliar vascular bundles, c. Leaves. 
d. Cellular medulla, e. Delicate parenchyma of middle bark, f Rem¬ 
nant of the bast-layer of the outer bark. Enlarged 3 diameters. 
Fig. 4A Portion of a vessel of the vascular cylinder, a. Transverse Lignine bars. 
6. Longitudinal threads of Lignine. 
MDCCCLXXX. 3 Y 
