OF THE FOSSIL PLANTS OF THE COAL-MEASURES. 
339 
zone it bends outwards horizontally and almost at a right angle to its former course, 
to reach the middle bark, where it again ascends obliquely outwards to reach the 
leaves. This is the course followed by each one of the numerous bundles seen in 
fig. 34. 
On comparing the above facts with what I have already described in my third 
memoir,* we cannot fail to see that though the exogenous cylinder of Lepidodendron 
selaginoides is much less developed than in the conspicuously Diploxyloid Burntisland 
plant, the essential conditions in each are absolutely identical. Thus figs. 35 and 36 
of the present memoir are virtually copies of figs. 10 and 13 of the older one, just as 
all the sections of the leaf bases of these two plants equally demonstrate their true 
Lepidodendroid character. Here, then, we have two Lepidodendroid plants which 
possess, in different degrees of development, the vascular organization which 
M. Brongniart believed, and which his disciples still believe, to be characteristic 
of Sigillarians plants, and which, on the evidence of that organization, they regard as 
Gymnospermous Phanerogams. Much too clear headed not to see the force of this 
kind of evidence, M. Grand-’Eury endeavours to evade the inevitable conclusion to 
winch it leads by saying, “ Tout cela ne prouve qu’une chose ; c’est que certaines 
impreintes de Lepidophloyos peuvent appartenir a des vegetaux Dicotyledones.” 
Bemembering the absolute identity in all the other features of the stems of Lepido- 
dendra and Sigil larise, and which identity M. Grand-’Eury has acknoviedged to 
exist, is it not more rational to admit that some of these arborescent Lycopodiacece 
have been provided with a pseudo-cambial layer from winch they developed an 
exogenous zone, than to transfer the genus Lomcitophloios from the Lycopodiacese 
with which all authors agree to arrange it, to the very different Phanerogamous 
Gymnosperms with which M. Grand-’Eury would thus unite it. My indisputable 
facts stand in the way of Brongniart’s hypothesis, which M. Grand-’Eury adopts in 
its totality, and, as it appears to me, he endeavours to evade them by the adoption of 
an explanation which has no foundation of fact on which to rest. 
The great misfortune has been that Lepidodendron Harcourtii was so long the only 
Lepidodendroid stem of which the organization was known, hence, instead of being 
rightly interpreted as one extreme modification of the Lepidodendroid type, of which 
Sigillaria presented the opposite extreme, it came to be regarded by M. Brongniart 
as the sole typical form. 
I need say little here about the views of Dr. Dawson on the affinities of Sigillarise. 
They have now advanced some way in the same direction as mine. He has discovered 
in Canada a Sigillaria with a true Diploxyloid axis, and which is very different from 
the type of Sigillaria that he has described in some of his earlier memoirs. This fact, 
and the study of a specimen of Lepidodendron Selaginoides which I forwarded to him has 
led him to the following conclusion, which I quote, because where so much discrepancy 
exists in the minds of some of those most experienced in the study of coal-plants, it is 
* Phil. Trans., 1872. 
