502 
PROFESSOR W. C. WILLIAMSON ON THE ORGANIZATION 
he would soon be induced to do so. It is clear to me that the separation of Calamites 
into two groups, the one Cryptogamic and the other Phanerogamic, the former repre- 
sented by Calamites and the other by Calamodendron, must be wholly abandoned. In- 
ternal organization affords no solitary fact upon which such a division can rest. The 
specimen illustrated in the figures 19-25 is one of the thin-walled types which M. Brong- 
niart, and those who hold his views, would regard as an unmistakable Calamites. Prior 
to his recent visit to England, Dr. Dawson held the views of the French botanist 
as strongly as he himself does ; and when he saw the specimen in question, he unhesi- 
tatingly identified it as one which was not a Calamodendron. It was this, and some allied 
examples, which led the Canadian geologist to declare to the Geological Society of London 
that “specimens in the collection of Professor Williamson show forms intermediate be- 
tween Calamites and Calamodendron , so that possibly both may be included in one 
family”*, — language which, when we remember the strength of Dr. Dawson’s previous 
convictions, bespeaks the true philosopher, to whom scientific truth is a sacred thing. 
The preceding descriptions and illustrations leave, I think, no reasonable room for dis- 
puting that the thin-walled and the thick-wooded plants, the latter being the Cala- 
modendra of Brongniart, are but different species of one group, if they represent more, 
in some instances, than different ages of the same species. 
The structure of the woody zone is unquestionably exogenous f. The arrangement of 
its vessels and medullary rays, its mode of growth, and that of its aerial branches all 
demonstrate the truth of my conclusions on this point. But the bark is the cellular 
covering of a Cryptogam. Whichever of the verticillate-leaved plants of the Coal-mea- 
sures constituted its foliage, they are all equally cryptogamic. My strobilus, the Cala- 
mitean character of which it is impossible to doubt, is filled with round spores that 
are unmistakably Cryptogamic. The structure of the roots affords clear evidence that 
they were not the woody prolongations of the main axis seen in the roots of the Gymno- 
spermous Conifers, but adventitious appendages of the Cryptogamic type. All these 
facts point to one conclusion, viz. that the Calamites were all Cryptogamic plants, but 
that they possessed a much higher organization than is seen in any of the Cryptogams 
living at the present day. Some writers affirm that the living Isoetaceae exhibit an 
exogenous stem. Since I have had the opportunity of studying them for myself, I must 
confess I have failed to trace the evidence of the alleged exogenous growth ; but the 
authority of Hofmeister and other botanists is sufficient to show that it exists; in 
the Calamites the proofs of such growth are incontrovertible. 
There is no question that the only living plants with which Calamites can be com- 
pared are the Equisetacese, with which Mr. Carrutiiers has unhesitatingly united them ; 
* Abstract of the Proceedings of the Geological Society of London, No. 217, May 1870. 
f I have already pointed out the resemblance which a transverse section of a Calamite, made at an internode, 
bears to a similar section of a branch of the first year belonging to any exogenous plant. The Calamite may 
be regarded as exhibiting permanently a condition that is temporary and transitional in the living plants. This 
observation has especial reference to the non-multiplication of the woody wedges after their first appearance in 
the stem of Calamites. 
