56 Correspondence. 
ing, in company with Dr. Stur of Vienna, and Mr. Seward of Cambridge 
the immense and critical collection of microscopic sections on which rest 
the statements which for the past twenty years Prof Williamson has put 
forward regarding the nature of the lepidodendrids and sigillarids. As is 
well known to all students of this department of science. Prof. W. has 
maintained almost single-handed against others the partly vascular nature 
of the stem of these great trees of the Coal Measures. Mr. Carruthers, of 
the British museum has been the most prominent leader on the opposite 
side. 
No one can, I think, rise from an examination of the beautiful series of 
slides which the industry of the professor has accumulated iu the course 
of a long life's work without feeling that the structure of these old trees 
was what he has afflrmed it to be. I was previously familiar with the 
engraved figures iu the proceedings of the Royal Society of London, but 
there always lurks a certain, or rather an uncertain, amount of doubt in 
regard to the "personal equation" of the observer. By an almost un- 
conscious omission, and an equally unconscious amount of commission, a 
drawing oft«n becomes a diagram and ceases to be truthful. It represents, 
not what the microscope shows, but what the observer saw, and these, as 
every microscopist knows only too well, are two distinct things. But 
after a careful examination of Prof. Williamson's material, no doubt can 
remain in the mind of the observer, that the existence of a true woody 
cylinder in both these genera is fully established. Abundance of teal 
fibre and of medullary rays may be seen in the sections of their stems 
which the professor has made . Many other points of which I have not 
the time to write just now, are also established by his work. We need no 
longer, therefore, hesitate to conceive of these giants of the palnaozoic 
forests as huge exogenous cryptogams containing in themselves the essen- 
tial structure of the Lycopodium and that of the dicotyledonous trunk of 
the present day. 
Soon afterwards I had also the pleasure of visiting Mr. R. Kidston of 
Sterling, another enthusiastic worker in the same field, whose beautiful 
collection of the same kind only confirms in the strongest and clearest 
manner what Prof. Williamson has published. Mr. K's results have been 
laid before the scientific world in a series of papers published in the trans- 
actions of the Royal Society of Edinburgh, and in the Quarterly Journal 
of the Geological Society ©f London. It is only fair to add that fortune 
has favored the workers on the other side in a singular manner by afford- 
ing them specimens of the coal plants in a state of preservation that renders 
them well adapted for the purpose of microscopic research. No similar 
specimens have, so far as I am aware, been yet discovered on this side of 
the Atlantic. Silicified and calcified fossil trunks of Lepidodendron and 
Sigillaria lend themselves easily to the work of the lapidary and the micros- 
copist, and though these are rare even in Europe yet they have been 
found in quantity sufllicient for the purpose. The pyritized remains of 
which such specimens usually consist in this country, though confirming 
the results above stated as far as their evidence goes, yet fall far short of 
the complete demonstration afforded by the transparent sections of Europe. 
