128 Contributions towards Esiablishing the General Character 
nally spaces, which, in addition to a large portion of cellular tissue, con- 
tained the vessels that passed into the external appendages; the term 
medullary ray is, therefore, inapplicable to them, and asa substitute that 
of vascular passage is proposed.* 
In none of the longitudinal sections which have been published of 
Stigmaria are the fibril cords represented passing through the entire 
thickness of the cylinder, as the groove of the radiating plates indicates. 
I was in hopes of procuring some sections exhibiting this character, but I 
have not yet succeeded : nevertheless, a compressed specimen in my col- 
lection, containing an impression of the cylinder, is of considerable value 
in the absence of such sections: the tissue has disappeared, but the 
impression remains, which is so complete that the arrangement of the 
tubes is clearly exhibited. Most of the tubes run perpendicularly up the 
cylinder, as represented by a, bin fig. 2, Plate V., but occasionally they 
are seen curving away from the place originally occupied by the pith c, 
in the manner shewnat f. There can be no doubt that the curving tubes 
constitute the fibril cords of this specimen. 
In connection with these cords two or three questions arise, which re- 
quire a little of our attention. What do they originate from ? Do they 
strike off from the tissue of which the principal part of the eylinder is 
composed ? or do they belong to an independent system, as is the case 
with their analogues in Anabathra? From his description of the figures 
which represent the internal structure of Stigmaria, it may be supposed 
that Brongniart adopts the view involved in our second question ; for, in 
speaking of the fibril or vascular cords, it is stated that they separate 
themselves from the tissue of the cylinder. Notwithstanding the weight 
of this opinion, coming, as it does, from so eminent an authority, I may 
be pardoned hazarding one that is totally different, to the effect, that the 
-cords belong to a system distinct from the tissue which forms the prin- 
cipal part of the cylinder. There can be no great objection, it is pre- 
sumed, to take as granted that Stigmaria is the root of Sigillaria. Now 
the sections which have been published of the last plant clearly shew that 
its circle of apparently isolated bundles is distinct from the enclosing 
cylinder ; and it is equally obvious that the former constitutes the me- 
dullary sheath, and the latter the ligneous system. If a distinction of 
this kind exists in the stem, why, it may be asked, ought not the 
same distinction to prevail in the root? Again, the leaf cords of 
Sigillaria, as admitted by Brongniart, evidently spring from the medul- 
lary sheath, and not from the radiated cylinder,—why then may not 
the fibril cords of Stigmaria be independent of the radiated cylinder 
which they traverse? But it may be urged that this fossil does not shew 
* The short tabular description given by Brongniart of the anatomy of Sem- 
pervivum, (“ Observations,” p. 438), induces me to think that the name here used 
will not be objected to ; since it is stated that the plant is “ without medullary 
rays, but offers some spaces for the passage of the vascular bundles of the leaves.” 
2 
a), ee a 
