Seward .- — The Anatomy of Lepidodendron aculeatum , Sternb. 3 79 
dissents from Prof. Weiss’s interpretation of the tuberculated branch, 
expresses the opinion that the anatomical characters are not identical with 
those of the true Lepidodendron fnliginosum , though he recognizes that 
Weiss’s specimen belongs to the same type of structure as the vascular 
axis of that species. The differences mentioned by Kidston do not 
appear to me of sufficient importance to serve as an objection to the use 
of the term L. fnliginosum on anatomical grounds ; but the more important 
point is, the existence of this type of anatomical structure does not 
necessarily imply that the stem exhibiting it possessed the surface features 
of Lepidophloios. Mr. Kidston regards the tuberculated specimen as 
a fertile branch of Sigillaria discophora (Ulodendron minus). It would 
lead us too far afield to enter into the arguments for or against the reference 
of the fertile branch to Lepidophloios , but the foregoing description justifies 
the view that on anatomical evidence alone we cannot in the present state 
of our knowledge safely assume that the type of structure described 
by Williamson as Lepidodendron fnliginosum is the exclusive possession of 
Lepidophloios. Dr. Scott gave expression to this view when he wrote : — 
‘ So far as is known, however, there is no constant difference in internal 
structure between Lepidophloios and Lepidodendron V 
Without discussing the value of the presence of Halonial tubercles 
as a mark of distinction between Lepidophloios and Lepidodendron , 
I submit that it is better to refrain from attempts to separate these two 
genera on purely anatomical evidence. The fragmentary nature of our 
material and the almost constant absence of external features in the case 
of petrified specimens are obstacles in the way of satisfactory identification 
and correlation ; it is better to recognize the limitations imposed by 
imperfect knowledge, and to rest content with the application of specific 
terms to anatomical types without regard to those rare cases in which 
external and internal characters are supplied by the same specimen. The 
same anatomical type, or rather what the fragments at our disposal lead 
us to regard as the same type, does not necessarily imply identity in 
external features. Our acquaintance with the anatomy of Palaeozoic 
Lepidodendreae is much too meagre and superficial to enable us to judge 
of the degree of correspondence between the two kinds of characters 
available for specific definition. I would therefore speak of the specimen 
described above as belonging to the type Lepidodendron fnliginosum , a type 
of structure which occurs in association with Lepidophloios as well as with 
Lepidodendron leaf-cushions. 
The present state of our ignorance on many histological points 
connected with the Lepidodendreae as well as in regard to grosser 
anatomical characters affords a strong plea for a thorough comparative 
examination of the Palaeozoic Lycopods. 
1 Scott (’00), p. 123. 
