OF THE FOSSIL PLANTS OF THE COAL-MEASURES. 
535 
supposition that each of these Traquarice was a spore, and as such, primarily a single 
cell, it was easy to regard the branching tubes as outward extensions of the spherical 
exosporium, originally the outer cell-wall of the organism. The development of the 
remarkable ramifications of the sporocarp of the Fungoid Phycornyces nitens, described 
by Professor Bornet/" appeared to furnish an illustration of the mode in which these 
radiating and branching extensions had been formed, but in the latter example the 
central stem of each branch-system opens at its base by a wide communication with 
the central cell cavity of which its tubules are but extensions. When describing 
fig. 43 (p. 513) I pointed out that the specimen there delineated appeared to favour a 
similar explanation, but those now described seem to tell a different story. It will be 
seen that the bases of each of the three principal stems, b, b', and b'", ate closed and 
not open. I have examined every available specimen of Trciquaria in reference to this 
point with the utmost care, but they all seem to lead to the same conclusion, viz. : 
that in their matured state each of these branching spines is closed at its base and 
thus assumes the form of a separate, unicellular, branching trichome; that they are 
really trichomes is, however, too improbable to be accepted as true. Hence the only 
conclusion at which I can arrive at present is that they were primarily mere extensions 
of the exosporium, but that when this exospore became differentiated into two layers 
and the outer one developed its remarkable system of branching tubes, the latter organs 
became separated from one another and each had its basal aperture closed in by the 
contraction of that part of its exosporial wall; the inner layer of the differentiated 
exosporium meanwhile retaining its primary simplicity as a thin spherical cell-wall. 
Another feature of interest in these objects is the condition of the cells contained in 
the interior of several of the macrospores. The modification of the endosporal cells 
seen in some of the recent Selaginellce, especially the large cells which Pfeffer not 
only compares with the endospermic cells of Angiospevms, but even designates by 
the same name, invest the study of these ancient forms with importance. I have now 
met with nine examples of these Traquarian macrospores containing cells. Some of 
these are already represented in figs. 42 and 45. 
I find several modifications in the cellular contents of these spores, which are 
probably significant. In one to which I will refer as A (fig. 45), the endospermic 
cavity is filled with comparatively large, thin-walled cells, which compress each other so 
closely as almost to constitute a loosish parenchyma, their individual diameters being 
about ’0036 ; none of these cells display any definite organised contents. In specimen 
B, for which I am indebted to Mr. Spencer, of Halifax, the endosperm consists of 
similar cells, though of smaller size, having a diameter of from '0011 to *0015. Most of 
these are like those of specimen A, though less closely packed, and about six of them 
contain each a single small, round, dark-coloured cell, having a diameter of about *00036. 
A third specimen, C, which I obtained from Mr. Binns, of Halifax, is filled with similar 
thin-walled transparent cells (diameter '0014, '0015), but now every cell contains one 
* ‘Annales des Sciences Naturelles,’ 5 e serie, tom. 17, pi. 20, figs. 7-13. 
3 z 2 
