132 Contributions towards Establishing the General Character 
these fossils, is common to a large division of the vegetable kingdom ; 
and as respects the netted form of the vascular cylinder, it will presently 
be seen that we have become possessed of a means that will aid us in 
our present investigations. 
Let us now examine those Monocotyledons in which the bundles are 
less numerous than usual, and more regularly arranged than ordinary. 
A transverse section of the axis of a Fern, whether creeping or arbor- 
escent, exposes a number of apparently isolated bundles arranged in a 
circle, and imbedded in a mass of cellular tissue, (vide fig. 4, a, Plate V.) 
These bundles are composed of what are generally termed scalariform 
vessels, and of a fibrous form of parenchyma which envelops the 
former in the manner of a slieath. As these bundles are in connexion 
with the leaves, and are evidently analogous in function to those which 
form the medullary sheath of exogenous plants, they may be safely con- 
sidered as constituting the vascular system. : 
For a considerable time I was at a loss to know the exact longitudinal 
arrangement of the vascular bundles in the stem of a tree-fern. After 
many attempts to procure a specimen sufficiently long for the purpose, 
and after consulting a number of botanical works, I was on the point of 
relinquishing the inquiry, possessed of no other information than that in- 
cidently given by Brongniart, to-wit, that ‘‘the bundles anastomose at cer- 
tain distances,” (‘‘ Observations”) when it occurred to me that Aspidium 
Filix Mas might afford all the information that was desired. This led me 
ta dissect the rhizome of the fern just named. By this means, I ascertained 
that although the bundles appear to be isolated on the transverse section, 
as represented in fig. 4, Plate V., they are in reality all connected with 
each other at regular distances in the longitudinal sense, so as to form 
a netted cylinder, remarkably regular in its meshes. Fig. 5, Plate V., 
represents a portion of this cylinder rather enlarged, which I succeeded 
in clearing of its matrix of cellular tissue, after exhausting somewhat 
more than an ordinary degree of patience. As previously stated, I have 
not been able to study the longitudinal arrangement of the bundles of 
the trunk of a tree-fern; but I have little or no doubt that it is the 
same as in Aspidium Filix Mas. Probably in some arborescent forms of 
rapid growth, the meshes are narrower, more irregular, and very much 
elongated, which will cause the vascular cylinder to have very little of 
a latticed appearance. ! 
Reflecting on the fact of which we have just come in possession, that 
the bundles of the vascular system of Ferns and Conifers are connected 
with each other at certain points, so as to form a netted cylinder, more 
or less decided, it seems but fair to infer, that the apparently isolated 
bundles composing the medullary sheath of Sigil/aria elegans are simi- 
larly connected; and, owing to their regularity on the transverse sec- 
tion, it may also be inferred, that they form a similarly constructed 
cylinder. It is diffieult to conceive any objection to snch a conclusion. 
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