103 
and Affinities of Nematoffiiycus Logani. 
the name of Prototaxites Logani, and which Principal Dawson 
affirmed, in his Bakerian lecture before the Royal Society, to be the 
oldest known instance of coniferous wood, Mr. Carruthers has dis- 
covered that they are really the stems of huge Algae, belonging to 
at least more than one genus. They are very gigantic when 
contrasted with the ordinary Algae of our existing seas, nevertheless 
some approach to them in size is made in the huge and tree-like 
Lessonias which Dr. Hooker found in the Antarctic seas, and which 
have stems about 20 feet high, and with a diameter so great that 
they have been collected by mariners in these regions for fuel under 
the belief that they were drift-wood. They are as thick as a man’s 
thigh.”* 
This paragraph came under the notice of Dr. Dawson in a 
reprint in the ‘American Naturalist ’ for May, 1871, and he met it 
with the following reply : — 
“ The earliest known Coniferous Tree. — Allow me to say, with 
reference to a notice copied in your May number from the 
‘Academy,’ that the opinion respecting the plant above named, 
attributed to Mr. Carruthers, is an entire mistake. Prototaxites 
Logani is an exogenous tree, with bark, rings of growth, medullary 
rays, and well-developed, though peculiar woody tissue ; and if 
Mr. Carruthers has made such a blunder as that attributed to him, 
this can only be excused by defective observation or imperfect 
specimens. — J. W. Dawson.” f 
Unwilling to continue a discussion after this fashion, and aware 
that Dr. Dawson proposed publishing a further account of the 
Devonian plants of Canada, I addressed to him a letter, containing 
at length my interpretation of the structure and affinities of this 
fossil, with the view of preventing the republication of obvious error. 
I regret that my effort was futile. In 1871 Dr. Dawson published, 
as a Report to the Director of the Geological Survey of Canada, his 
work on ‘ The Fossil Plants of the Devonian and Upper Silurian 
Formations of Canada. ’J All the errors of observation which I 
had pointed out to Dr. Dawson in his own specimens when he was 
in London, and shown in detail by drawings and descriptions in the 
letter to which I have referred, are here repeated and expounded, 
and the same absurd generalizations as to affinities, &c., are indulged 
in. My communication is made the subject of the following note 
on page 19, and this is the only use made of it : — “ Mr. Carruthers 
has kindly pointed out to me some structural points in which this 
remarkable plant resembles Algae of the family Codieee , the long 
tubes traversing which he compares with the cells of Prototaxites. 
For the reasons stated in the text, however, I cannot accept this as 
an indication of true affinity, and must believe the plant to have 
been a terrestrial tree exogenous in its mode of growth. The high 
* ‘Academy,’ Oct. 1870, p. 16. f ‘American Naturalist,’ vol. v., p. 2d5. 
\ Quoted in this paper under the title ‘ Pre-carboniferous Plants.’ 
