ly entire, but in some instances
ranged in two, or even three, concentric lines round the depressed
centre of the areolae; while the interspaces outside are occupied by
numerous fretted markings, resembling broken fragments of petals, which,
though less regularly ranged than the others, are effective in imparting
a richly ornate aspect to the whole.

[Illustration: Fig. 125.]

[Illustration: Fig. 126.

STIGMARIA.]

[Illustration: Fig. 127.

THE SAME, MAGNIFIED.]

Ever since the appearance, in 1846, of Mr. Binney's paper on the
relations of stigmaria to sigillaria as roots and stems, I have been
looking for distinguishing specific marks among the former; and, failing
for a time to find any, I concluded that, though the stems of the
sigillarian genus were variously sculptured, their roots might in all
the species have been the same. The present rich specimen does seem,
however, to bear the specific stamp; and, from the peculiar character of
the termination of another specimen on the table, I am inclined to hold
that the stigmaria may have borne the appearance rather of underground
stems than of proper roots. This specimen suddenly terminates, at a
thickness of two and a half inches, in a rounded point, abrupt as that
of one of the massier cacti; and every part of the blunt sudden
termination is thickly fretted over with the characteristic areolae. The
slim tubular rootlets must have stuck out on every side from the obtuse
rounded termination of this underground stem, as we see, on a small
scale, the leaflets of our larger club mosses sticking out from what are
comparatively the scarce less abrupt terminations of their creeping
stems and branches. In at least certain stages of growth the sub-aerial
stems of Lepidodendron also terminated abruptly (see Fig. 24); and the
only terminal point of Ulodendron I ever saw was nearly as obtuse as
that of Stigmaria.

[Illustration: Fig. 128.

STIGMARIA.]

I have been long desirous of acquainting myself with the true character
of this latter plant (Ulodendron), but hitherto my labors have not been
very successful. A specimen of _Ulodendron minus_, however, now on the
table, which I disinterred several years ago from out a bed of
ferruginous shale in the Water of Leith, a little above the village of
Colinton, exhibits several peculiarities which, so far as I know, have
not yet been described. Though rather less than ten inches in length by
about three inches in breadth, it