Weiss. — A Stigmarici with Centripetal Wood. 223 
‘ Studies in Fossil Botany,’ p. 227.) The layers of cells, which must have 
clothed the periderm on the outside (outer cortex), whether a Stigmarian 
or Lepidodendroid axis, have entirely disappeared : only in one or two 
places does one find remains of small rounded cells of the nature of a 
primary cortex. They are much compressed, and their very poor preserva- 
tion points to their having been of soft and yielding character, like the 
outer cortex of a Stigmarici, and not of the hard dense nature one finds 
in the aerial stem of a Lepidodendron or Sigillaria , and particularly of 
Bothrodendron . Here and there a somewhat denser group of primary cells 
has been preserved, and these evidently represent the remains of a rootlet- 
cushion. The presence of these rootlet-cushions, taken in conjunction with the 
general absence of a resistant outer cortex, the very extensive circumference 
of the periderm as contrasted with the small diameter of the vascular axis, 
and the peculiar structure of the periderm cells, all go to prove the Stig- 
marian nature of the specimen. Of the rootlets which it bore, nothing 
definite can be said, as none are found in continuity with the specimen. 
The numerous rootlets, which surround the axis, are not of any one particu- 
lar type, and they may, of course, belong to other neighbouring Stigmarian 
axes. Indeed the very bad preservation of the softer tissues of the speci- 
men before us would seem to indicate that it had been dead long before it 
became petrified, and was invaded by the rootlets of surrounding plants. 
As is usual in Stigmarian axes, the tissues lying between the periderm and 
the vascular cylinder are very defective. One would indeed not expect 
them to be well preserved in a specimen in which the outer cortical tissues 
were destroyed. As a matter of fact the space within the periderm has 
been largely invaded by Stigmarian rootlets, and only here and there are 
found dense brown masses, consisting probably of the debris of the delicate 
middle cortex. In certain places there are more or less irregular patches of 
wide and short reticulate tracheids (see Fig. 7 , PL XV), which seem to have 
some connexion with the rootlet bundles, in connexion with which they will 
be referred to again. It is interesting to note that similar reticulate cells 
were described by Renault (’ 93 ) 1 in the cortical region of Stigmaria Brardii. 
As figured by him, however (PI. XXXIX, Fig. 14), they appear more fusi- 
form, as he indeed describes them to be, and they were found according to 
his description among the periderm cells, and not in the inner parenchyma- 
tous zone (middle cortex), which seems to be their position in the specimen 
under consideration. Indeed they are not only found in the outer portion 
of the middle cortex, but are present in large numbers close up to the vas- 
cular cylinder. This position may not be quite a normal one, as these 
tracheids have no doubt been displaced owing to the decay of the softer 
tissues, but there can be no doubt that they were associated with the 
vascular bundles within the soft, middle-cortex region. 
1 P* x 95- 
