OP THE FOSSIL PLANTS OF THE COAL-MEASURES. 
511 
of parenchyma, the cells of which appear as if slightly thickened at their angles. 
Under a low power these dark angular points are the only portions of the cells that 
are visible. The outermost of these cells have a mean diameter of "0022, but they 
become smaller as they approach the inner boundary of the tissue where many of 
them have less than half that size. The outermost layer of this organism is very 
peculiar. I have already observed that the periphery of the middle layer is an undula¬ 
ting one. Each of its peripheral projections sustains a cluster of very large thin- 
walled cells, d, d, most of which are prolonged radially. Each interval between these 
projecting cell-clusters is occupied by a single row of very strongly-marked, thick- 
walled cells, c, which appear to be modifications of the inner parenchyma, but whose 
entire cell-walls are thickened to form a protective layer at the depressed points of the 
surface of the organism. I find no trace whatever of any epidermal or other layer 
external to the large cells, d, and the obviously protective character of those marked c 
makes it clear that this is not an organism torn from its surroundings, but that we 
have substantially its true peripheral outline. There are some features of resemblance 
between the layer, b, and the cells, a, of fig. 38, hence it is not impossible that they 
may ultimately prove to belong to the same, or at least to allied plants. I propose 
to designate fig. 39 by the provisional name of Sporocarpon ornatum. One common 
feature characterises the whole of the objects which I have included in the provisional 
genus Sporocarpon, viz.: they exhibit no trace of having possessed any peduncular 
appendage wherewith to be attached to their parent plants. 
Wide diversity of opinion has long existed between Mr. Carruthers and myself 
respecting the next specimens to be described. At the meeting of the British Associa¬ 
tion for the Advancement of Science held at Bristol, Mr. Carruthers described some 
small objects from the lower Coal-measures of Lancashire, to which he gave the name 
of Trcicpiaria, and which he believed to be carboniferous Radiolarians. An abstract 
of his communication appeared in the Report of the Association for 1872.* Having 
examined specimens of these objects in my own cabinet in 1874, I ventured to doubt 
their Radiolarian character, and suggested! that they bore more resemblance to some 
Cryptogamic spores than to the marine siliceous Protozoa with which Mr. Carruthers 
associated them. The study of a fine series of these objects so far confirmed my con¬ 
victions that I presented a communication to the British Association at its Dublin 
meeting held last summer, in which I assigned what appeared to me sufficient reasons 
for regarding them as reproductive organisms belonging to some unidentified Crypto¬ 
gamic plants. I next forwarded the more important of my specimens to our highest 
authority on the subject of the Radiolarians, viz.: Professor Haeckel, of Jena, who, 
in addition to his own careful study of them, kindly invited his colleague, Professor 
Strasburger, to examine them along with him. Both these distinguished biologists 
have arrived at the same conclusion as myself respecting them, viz.: that they are 
* Trans, of Sections, p. 126. 
t Phil. Trans., 1874, Memoir, Part V., p. 56. 
3 U 2 
