378 Seward . — The Anatomy of Lepidodendron aculeatum , Sternb. 
cortical tissue is seen at a } Fig. 2, PI. XXVI ; the secretory strand and 
xylem with the intervening cambiform cells are shown at s, x and b. 
The two dark strips extending from the surface of the section seen in 
Fig- 5) c > and converging in the inner cortex consist of partially destroyed 
tissue bounded externally by cortical cells characterized by the presence of 
numerous secondary septa parallel to the wounded surfaces. The area 
between the two dark lines in the cortex is partly occupied by shrunken 
and isolated cells, which appear to have fallen apart as the result of the 
destruction of the middle lamellae. The xylem-ring internal to the injured 
region exhibits the normal structure. 
The anatomy of the specimen (Fig. 1) possessing the surface characters 
of Lepidodendron aculeatum exhibits an exceedingly close agreement with 
that type of structure which it has been customary to describe as 
Lepidophloios fuliginosus . So far as I am aware the only reference to 
the structure of Lepidodendron aculeatum previously published is by 
Prof. Bertrand who has mentioned the occurrence of petrified portions of 
suberous tissue in the nodules of Hardinghen, which are probably referable 
to this species. It has been pointed out by Weiss that the leaf-traces in 
the stem described by him as a biseriate Halonia,and referred on anatomical 
grounds to L. fuliginosus , pursue an almost horizontal course in the middle 
cortical region 2 : this is also the case in sections of other specimens of the 
same type which I have had an opportunity of examining. The steeply 
ascending course of the traces in the branch of Lepidodendron aculeatum 
(Text-fig. 3) constitutes a distinguishing feature — of how much value it is 
difficult to say. A comparison of the previously published figures of small 
branches of Lepidodendron fuliginosum with those given in this paper 
demonstrates a striking similarity which, with the exception of the course 
of the leaf-traces, seems to amount to identity. The age of the branch 
does not enable us to say anything as to the nature of the secondary 
xylem, which in older specimens constitutes a characteristic peculiarity of 
L . fuliginosum . 
Such evidence as is available would seem to point to the absence 
of trustworthy criteria enabling us to separate, on anatomical grounds, 
Lepidophloios and Lepidodendron. Weiss refers his biseriate Halonia to the 
former genus c on the strength of its internal structure 5 3 , but it is question- 
able whether the present state of our knowledge of lepidodendroid anatomy 
is sufficiently accurate to render this argument valid. Mr. Kidston, 4 who 
1 Bertrand, Cornaille and Hovelacque (’97), p. 491 ; Bertrand (’99), p. 391. 
2 Weiss (’03), p. 223. 
3 Weiss (’03), p. 220. It should be mentioned that Prof. Weiss (Joe. cit .) adds :■ — ‘as, however, 
an identification based solely on the internal structure might be disputed by some, I would seek to 
strengthen my conclusion by evidence from specimens showing external markings which can be 
identified with Lepidophloios and which at the same time possess only two rows of tubercles.’ 
4 Kidston (’05), p. 538. 
