162 
On the History, Histological Structure, 
that the cells are “much thickened by a ligneous deposit;” hut any 
one accustomed to the investigation of fossilized tissues will, on 
a hasty glance at Dr. Dawson’s figures, see that he has mistaken 
the nearly complete filling up of the cell-cavity with mineral matter 
for “ ligneous deposit.” This condition of fossilization is very 
common ; hut the close affinity, if not identity, of N. crassum 
with Prototaxites is almost admitted in the ‘ Pre - carboniferous 
Plants,’ where it is said : — “I place these plants here simply 
because of the resemblance of their tissues to those of Prototaxites, 
with which it is possible that they may have had some connection, 
being perhaps stems or slender roots of similar species of smaller 
size” (p. 20). 
When Dr. Dawson visited England in 1870 I had an oppor- 
tunity of examining, in his company, his specimens of Prototaxites . 
I then pointed out to him some peculiarities in its structure incon- 
sistent with his descriptions. He presented some of his very 
interesting fossils to the British Museum, and among the specimens 
of Prototaxites was one fragment which he specially pointed out as 
suitable for microscopic preparation and examination. The draw- 
ings accompanying the present paper have been accurately made by 
Mr. Blair from this specimen. 
In a paper “ On the History and Affinities of the British Coni- 
fer ee,” which I submitted to the Geological Section of the British 
Association at Liverpool (1870), I had, in dealing with the Taxinese, 
to consider Prototaxites, which Dr. Dawson informed me he had 
found in England. A careful examination of the prepared speci- 
mens had convinced me that Dr. Dawson’s plant was no conifer, and 
reasons which I shall presently state at length satisfied me that it 
was an Alga. This opinion I expressed as a reason for my elimi- 
nating Prototaxites from the Taxineie, as is shown in the only 
abstract of my paper published at the time, from which I make the 
following extract: — “The Taxineie, containing nearly 100 living 
species found all over the world, and represented in Britain by the 
yew, made their appearance in the Carboniferous rocks, as deter- 
mined by a fruit described by Dr. Hooker, and shown by him to be 
nearly related to the living Salisburia. The supposed Taxineous 
wood from the North American Devonians, to which Principal 
Dawson gave the name of Prototaxites , was a remarkable Alga of 
enormous size. Several Taxineous fruits have been found in the 
Eocene strata at Slieppey.”* 
The reporter of another scientific journal, impressed apparently 
with the notion that this was the one point of interest in my com- 
munication, gave the following paragraph as his only account 
of it: — 
“ Colossal Fossil Sea-weed. — From the microscopic examination 
of the structure of specimens of the fossil trunks described under 
* ‘Nature,’ Oct. 6, 1870, p. 464. 
