OF THE FOSSIL PLANTS OF THE COAL-MEASUIiES. 
335 
Calamites, whereas I have most strongly opposed that idea,'" on the identical grounds 
recognised by Dr. Brown in the case of Triplosporites, viz., that there must be a 
correspondence between the internal structure of the stem and that of the axis of the 
strobilus whenever the two belong to the same plant, which correspondence not only 
does not exist in the plants in question, but is as remote as possible from doing so. 
Lepidodendron and Sigillaria. 
Notwithstanding all that has been done in elucidating the relations of these two 
groups of plants much still remains obscure. The present position of the question 
appears to be this. The first stem of a Lepidodendron discovered, in which the 
internal organization is preserved, was that historic one originally described and figured 
by Witham,! and named by him L. Harcourtii. The same specimen was further 
described and figured by Bindley and Hutton, J and again by Brongniart. § This plant, 
which in my opinion only represents one extreme modification of the Leptdodendroid 
organization, and that the least highly organized one, was for so long a time the only 
known example in which the internal structure was preserved, that it came to lie 
regarded, especially by Brongniart and those who implicitly accepted his conclusions, 
as typical of the entire Lepidodendroid group. In the volume which contained his 
description of his Lepidodendron , Wtt ham described his Anahathra pulcherrima (Joe. 
cit., p. 74, plate 8, fig. 7-12), a plant which, as we now know, only differs from the 
Lepidodendron in having a second exogenous vascular zone, enclosing the primary 
one of the Lepidodendra. Witham does not hazard any opinion as to its botanical 
affinities. Brongniart ignored this plant in his ‘Vegetaux Fossiles,’ but at a later 
period he obtained a specimen which he made the subject of his classic memoir on 
Sigillaria elegans. || This latter plant possessed many of the features of Witham’s 
Anahathra, but exhibited some differences in the structure of its inner vascular 
cylinder, which in Sigillaria elegans consisted of an interrupted vascular ring, whilst 
the Anahathra displayed a continuous one. Then followed the publication of Corda’s 
‘ Flora cler Vorwelt,’ in which the author describes his genus Diploxylon, a form which 
unites the features of Lepidodendron Harcourtii with those of Sigillaria elegans, 
having the continuous inner vascular cylinder of the former associated with the 
exogenous zone of the latter. In his ‘ Tableaux cles genres de Yegetaux Fossiles,’ p. 57, 
Brongniart very properly places Corda’s genus Anahath ra amongst his “ Sigillariees,” 
and with equal accuracy identifies it with the Anahathra of Witham. Various other 
publications by Dr. Dawson, Mr. Binney and myself have followed those quoted, 
* See my fifth memoir, Pliil. Trans., 1874, p. 65. 
t ‘ The Internal Structure of Fossil Vegetables, &c.,’ 1833, p. 51, plate 13. 
X ‘ Fossil Flora,’ tom. ii. p. 45, plates 98 and 99. 
§ ‘ Vegetaux Fossiles,’ p. 38, plates 20 and 21. 
|| Arch. Mus., tom. i. p. 405, plates 25-28. 
MDCCCLXXV111. 2 X 
