OF THE FOSSIL PLANTS OF THE COAL-MEASURES. 
509 
cells arranged with the regularity of ordinary parenchyma, it further shows the pro¬ 
longed hairs to be much more numerous than in any of the specimens previously 
described—indeed, in several portions of the section they are developed from every cell. 
Fig. 29 represents an almost superficial tangential section of the Sporocarpon 
cellulosnm of my previous memoir. The numerous component cells constituting its 
wall are of nearly uniform size, and arranged with parenchymatous regularity. The 
dark zone marks the boundary of the central cavity into which we look through the 
small central orifice, where the section has sliced off the most prominent part of the 
sphere. On the opposite side of the slide the section has passed nearly through the 
centre of this cavity, the maximum diameter of which corresponds with the outer 
boundary of the dark zone. On employing a one-eighth oil-immersion lens, we dis¬ 
cover that the free or peripheral extremities of most of the cells are slightly prolonged 
into small, dark-coloured mammillae, as represented in fig. 30. 
Fig. 31 is a transverse section of an important specimen, since it seems to indicate a 
connexion between figs. 29 and 24. It reveals the cells of the boundary wall in every 
stage of transition from the form seen in fig. 29, to those elongated into the radiating 
hairs of fig. 24. Thus at a the terminal mammilla of fig. 30 is becoming slightly 
elongated, at b it is yet more drawn out, and at c it has nearly assumed the full 
dimensions of the hairs of figs. 24, 25, and 26. 
Like fig. 25, the interior of fig. 31 is filled with large cells, averaging about ‘0025 
in diameter. 
This fine series of illustrations suggests the possibility that these objects are 
cellular spheres, the cells of which were in the first instance short, and compactly 
grouped ; but that as their growth advanced the peripheral extremities of many of them 
became prolonged into hollow and extremely brittle hairs, and that as this growth 
progressed further, a small number of large cells appear in the inner cavity, and are 
gradually developed mto a large number of small ones, like those which occupy the 
interior of fig. 69a of my ninth memoir. On applying the oil-immersion one-eighth 
objective to the latter specimen, I discovered that many of its contained cells displayed 
the features represented in figs. 32, 33, and 34. The protaplasms of 32 and 34 have 
subdivided to form four daughter-cells, whilst fig. 33 contains two such cells. Whether 
these are the ultimate spores, or whether they are destined to be the mother-cells of 
yet further developments, it is impossible to say ; but seeing that in the only specimen 
in which these spore-like objects have been found the sphere-wall has attained the fullest 
development with which we are acquainted, whilst its subdivided cells are no longer free 
but are reduced to the state of a somewhat compact parenchyma, I think we have 
strong reasons for inferring that they are destined to be the true spores of the organism. 
Of the specimens just described I am indebted to Mr. Binns for the slides con¬ 
taining figs. 24 and 29, to Mr. Earnspiaw for 25, 27, and 30, and to Mr. Spencer 
for 26. 
Two of the slides from Halifax, for which I am indebted to Mr. Spencer, contain 
3 u 
MDCCCLXXX. 
