130 Contributions towards Establishing the General Character 
are marked with transverse bars or lines which frequently run parallel 
to each other, but occasionally they anastomose so as to form reticu- 
lations. The tissue of the vascular system, on a general view, resembles 
the ligneous—consisting of transversely-barred elongated tubes. The vas- 
cular and the ligneous tissue are intermixed, which causes the former to 
follow to a certain extent the radial arrangement of the latter. The ligneo- 
vascular cylinder, as it may appropriately be termed, is furnished with a 
number of oblique spirally arranged oval-shaped spaces (¢), which com- 
municate with the pith on the one hand, and with the bark on the other, 
and which are principally occupied with cellular tissue.* From the yas- 
cular portion of the cylinder, numerous bundles (/) strike off, and pass 
through the cylinder, by means of the spaces, into the external appen- 
dages. Besides the vascular passages, as the oval-shaped spaces may be 
termed, the ligneo-vascular cylinder is intersected by a small number of 
thin cellular plates, which are clearly medullary rays (Brongniart). 
If the general character just given should ultimately prove to be cor- 
rect, it will follow that the principal difference between Sigillaria and 
Stigmaria is, not in the absence of the medullary sheath in the latter, as 
Brongniart supposes, but simply in the vessels of this sheath being inter- 
mixed with those which compose the ligneous system. 
The remaining portion of these contributions will be devoted to a 
consideration of the place which Sigillaria occupies in the vegetable 
kingdom. 
Previously to his discovery of its internal structure, Brongniart main- 
tained that Sigil/aria proximated to the tree ferns: this view, it is well 
known, was founded on external characters. The discovery alluded to, 
however, brought about a complete change in his opinion, so that he is 
now in favour of Sigillaria being allied to the Cycadeous Gymnosperms. 
The resemblance between the markings on its ligneous tissue and those 
which characterise certain of the vessels of Zamia integrifolia, and the si- 
milarity existing between the cylinder, as regards relativeness of size to 
other parts, of both plants, are considered as strongly in favour of the 
last opinion, From the strong presumptive evidences which have al- 
ready been adduced, in support of certain forms of Newropteris haying 
constituted the foliage of Sigillaria, it would appear, however, that the 
earlier view of Brongniart ought not to be so hastily rejected. Most of 
the arguments which have been advanced in the ‘‘ Végétaux Fossiles” in 
support of the view that Sigillaria is allied to the tree-ferns, are, in my 
opinion, as effective as ever, notwithstanding the cycadeous affinities 
of its internal structure, and the counter arguments which have been 
advanced by the authors of the ‘‘ Fossil Flora.” We will now pause 
* Owing to these openings or spaces, it is easy to conceive, that, if the vascu- 
lar tissue were separated from the ligneous, the medullary sheath would be in 
the form of a netted cylinder. 
