6 ARKIV FOR BOTANIK. BAND 10. w:o 15. 
sist of several rows of cells. On the impression, the sporangia 
appear oblong or obovate (pl. 1, figs. 7—10). There is no trace 
seen of a stomium, and it is not clear in what manner the de- 
hiseence took place. There is sometimes seen a radial split 
across the apex and continuing for some distance down, but it 
is not certain that this is an original feature: it may be only an 
effect of the pressure during the fossilization. The sporangia 
have no annulus; but there is a marked difference in the 
cellular structure in the lower and the upper parts of each spor- 
angium. The cells of the wall are often clearly seen, and in 
such cases, they are found to be, in the lower part of the sporan- 
gium, thin-walled and longitudinally elongate. In the upper 
part, they are shorter and pro- 
vided with thick walls. This upper 
zone of thick-walled cells is of 
varying breadth occupying 1/, to !/, 
of the sporangium, from the apex 
downwards, and always compri- 
sing several concentric rows of 
cells. "There is a more or less gra- 
dual transition between the upper 
zone of thick-walled/cells and the 
Fig. 1. lower part; but the former is at 
Schematic tears anowins the same time very marked, its 
disposition of sporangia. dark brown colour, caused by the 
thickness of the cell-walls, vividly 
contrasting with the lighter yellow of the lower part. The cells 
of the upper, darker zone diminish in size towards the apex. In 
a few cases the latter is of a lighter colour as if occupied by some 
few small thin-walled cells; but it was not possible to make 
out the structure with certainty (pl. 1, fig. 9). 
It was possible, by treating the carbonized remains in the 
usual manner, to observe the spores microscopically (pl. 1, figs. 
11, 12). These are rounded with a diameter of about 30 y. 
They have the typical triradiate markings, but otherwise they 
show no surface-sculpture of any kind. The number of spores 
in each sporangium could not be made out. 
Although information is still lacking on several important 
points, the structure and arrangement of the sporangia is now 
sufficiently well known to justify a discussion of the affinities 
of these fertile leaves. In the light of the present evidence it 
