OF COAL-MEASURE PLANT-IMPRESSIONS. 189 
II. LEPIDODENDRON LYCOPODIOIDES, Sternb., L. OPHIURUS, Brongn., 
and L. LORICATUM, sp. nova. 
1. INTRODUCTION. 
In the course of time, as the stuly of impressions of Coal-measure plants 
progresses, it has sometimes happened that doubts have arisen as to the exact 
nature of well-known species, which hitherto have been accepted almost 
without question. At first a mere suspicion arises as to whether such and 
such a plant is really identical with some ancient type in particular, and as 
to what exactly are the characters peculiar to it by which it is to be distin- 
guished from other somewhat similar but probably distinct forms. Such 
suspicion may increase until a stage of uncertainty is reached. Or, again, 
it may be borne in on the worker, as he comes to have access to an ever- 
increasing range of materials, that confusions have arisen between somewhat 
similar but perhaps distinct species. At length a time is reached when it is 
necessary to set these doubts at rest by means of detailed re-examinations of 
the particular plants in question. 
In the present notes I propose from time to time to give the results. of 
such critical revisions as have seemed to me necessary as the result of many 
years’ taxonomic experience of Coal-measure plants. 
In the present note I deal with two of our Coal-measure species of 
Lepidodendron—L. lycopodioides, Sternb, and L. ophiurus, Brongn.,—both 
of very common occurrence, and also with a third type, which it is proposed 
here to term L. loricatum, sp. nova. 
It appears to me that L. ophiurus has been largely confounded with 
L. lycopodioides, Sternb., and vice versa. Yet I hope to be able to show here 
that no grounds for such a confusion exist. 
Two facts of importance may first of all be emphasised here. The first of 
these is that the only characters which are of any critical value as a means 
of discriminating species of Lepidodendroid stems are those exhibited by 
specimens showing the true external features of the leafless stems in question, 
This fact is, of course, widely recognised among palæobotanists, but at the 
same time the opinion appears to be widely held that even specimens in 
which only the decorticated or subepidermal characters are exhibited can 
also sometimes be determined specifically. Or, again, it is urged that shoots 
entirely clothed with leaves can be identified. With these conclusions I am 
unable to agree (cf. 26. p. 150). I reject specific conclusions founded on 
such evidence. 
Secondly, there appears still to be a considerable confusion as to the 
detailed morphology of the persistent leaf-armour of such stems, the units of 
which, in. the leafless stems, are best described as leaf bases, though some 
prefer the term * leaf eushions." The matter is also frequently complicated by 
P2 
