On the History, dr., of Nematophycus Logcini. 
161 
8 pace which represents them in a tangential slice shows that they 
must have consisted of several rows of cells. The rings of growth 
are rather more than one-tenth of an inch in thickness, and they 
indicate, in a specimen 1 foot 5 inches in its greatest diameter, and 
11 inches in its least, an age of about one hundred and fifty years. 
In a subsequent communication to the Geological Society,* 
Dr. Dawson describes some fossils collected by a member of the 
Canadian Survey at Gaspe, and among them appears this same 
fossil under the name of Nematoxylon crassum, gen. et spec, nov., 
with the following description: — “Fragments of wood with a 
smooth thin bark, and a tissue wholly composed of elongated cylin- 
drical cells with irregular pores or markings. No pith, medullary 
rays, or rings of growth/’ With it are associated, in the same 
genus, some small stems named N. tenue, founded obviously upon 
fragments of wood, but which have nothing whatever to do with it, 
as Dr. Dawson’s figures clearly show. As Dr. Dawson has never 
given characters to any of the genera which he has proposed in his 
numerous papers, it would not be possible to determine what con- 
sideration induced him to place two structures so different under 
the same genus, but in this case he tells us he was influenced by the 
novel consideration that “they correspond in their negative cha- 
racters ” ! Such beautiful simplicity in the characters which unite 
species into genera ought greatly to simplify our systematic works ; 
indeed, I cannot understand on what principle Dr. Dawson, after 
establishing Nematoxylon, did not include all the fossils he has 
described in this remarkable genus. It certainly swallowed up 
Prototaxites. It is true Dr. Dawson points out four characters in 
which N. crassum differs from Prototaxites. These are: — 1st. The 
cells are one-third greater in diameter, — but in the drawings repre- 
senting the two fossils, in his recently-published ‘ Pre- 
carboniferous Plants,’ each being magnified to the 
same extent, the cells of N. crassum are the smaller 
of the two. This is obvious from an examination of the 
facsimile of Dr. Dawson’s figure of N. crassum here 
given (Fig. 1 a), as compared with a small portion 
of his figure of Prototaxites, also given in facsimile 
(Fig. 1 h). 2nd. The cells are destitute of the 
peculiar markings of Prototaxites , — but the cells of 
Prototaxites are also always destitute of the markings 
which Dr. Dawson describes as “peculiar” to them, frcSffig! 137 “^ 
as will be apparent from the description which , F f S baw^n“ ^ 2 e ? 
follows. 3rd. There are no medullary rays — neither p £^£ niferon3 
are there any in Prototaxites. And 4th. There are 
no rings of growth, — and this might have been expected, as the 
largest specimen was only half an inch thick. There seems to be 
something more in the character given in the general description, 
* 1S63, vol. xix., p. 4t6. 
Fig. 1. 
