33G 
PROFESSOR W. WILLIAMSON ON THE ORGANIZATION 
besides those of M. Renault and M. Grand-’Eury to which I shall have to refer more 
specially. But the point at issue resides in a nutshell. One school follows Brongniart 
in believing that Lepidodendron Harcourtii is the true typical representative of the 
structure of the Cryptogamous Lepidodendra, whilst Sigillaria elegans and Diploxylon 
represent the Sigillarise which are not only supposed to have no affinity with the 
Lepidodendra. but belong to the very different group of the flowering Gymnosperms. 
In several of my previous memoirs 1 have arrayed a series of facts which appear to 
me conclusive, and which lead me to reject this separation of the Lepidodendra from 
the Sigillariae, and I should have been inclined to have left those facts, and the argu- 
ments based upon them, to stand or fall by their own accuracy. But in his recent 
volume on the coal-measures of Central France, my friend M. Grand-’Eury has put 
my arguments in so erroneous a form, that I deem it necessary to correct the errors, and 
to advance additional evidence in support of my views. In my third memoir, I showed 
in a way which no one has attempted to answer, that, in its young state, the 
Anabathra of Witham is a true Lycopod, of the type of Lepidodendron Harcourtii. 
But that after a time, in addition to the inner ring of vessels characteristic of the 
Lepidodendron, it began to develop the outer exogenous ring characteristic of Brong- 
niart ’s family of Gymnospermous Sigillarice. The conclusion to which these facts 
lead us is inevitable, and the argument unanswerable, except it can be shown that 
I am mistaken hr my facts, which no one has even attempted to do. I have very little 
doubt but that this plant which M. Brongniart’s theory converts into a Cryptogam 
in its youth and a Phanerogam hr its mature life is really the Lepidodendron 
Veltheimianum. It must be understood that I have sought to demonstrate the 
organic unity of the Lepidodendra and the Sigillarise by showing that plants which are 
unquestionable Lepidodendra gradually acquire the internal features supposed to be 
characteristic of the Sigillarise. In the second of my memoirs,* I have shown that 
the bark of Favularia and of a true Sigillaria, have a structure which is identical 
with that of Lepidodendron, but this is only a secondary illustration of their unity, 
auxiliary to that based upon the development of then’ vascular axis. Such being the 
case, I was surprised to find in M. Grand-’Eury’s recently published work the following 
remark, “ M. Williamson dit avoir trouve une serie de specimens etablissant l’identite 
des Sigillaires avec les Lepidodendrons. En suivant son opuscule, on voit que hauteur 
passe a cette conclusion par des faits isoles, d’apres l’analogie de l’ecorce et non par des 
exemples complets reunissant les caracteres exterieurs aux caracteres interieurs” 
(loc. cit., p. 177). I have already said sufficient to show that tins paragraph involves 
a serious error on the part of its author, which is not removed by the remarks that 
follow it. On the same page as that from which I have quoted, M-. Grand-’Eury 
makes the important admission, “ II est au moins curieux que, a part le corps vasculaire, 
les autres parties des Sigillaires soient semblables aux parties correspondantes des 
Lepidodendrons,” and he further adds, “ Cette egale composition descend j usque dans 
* Phil. Trans., 1872, pp. 210 and 212. 
