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(From the Monthly Micrtncppib^f^Jbuctuil^: August, 1873.)

REMARKS ON MR. CARRUTHER'S VIEWS OF
PROTOTAXITES.

By J. W. Dawson, I.L D., F.Il.S.

In tii'! " Monthly Microscopical Journal" lor October, 1872,
Mr. Carrutlier.«. ^>t' tlic Biitit*li Muscuju, has published a paper
Id which he endeavours to show that my Prototaxites Logani,
from the Devonian of Gaspe, is a gigantic seaweed, for which he
proposes the generic name Ncm<itophycua. Though I .saw this
^ article some time ago, other avocations have prevented me from
attending to it until now.

The tone and manner of the article, 1 may s.ty in passing, are
unnecessarily ofFi'iisive; and the author bolsters up his argument
by unfair assumptions that I am ignorant of some of the most
familiar facts of structural botany, facts which were well known
to me while he was yet a school-boy, and which are stated or im-
plied in many of my papers on fossil plants. Possibly, however,
Mr. Carruthers is already aware of his bad taste in this matter,
and it will be to me a sufficiently ungracious task to expose, as t
must do in the interest of truth, the worthlessness of the expla-
nation which he offers of the nature of Prototaxites. I shall
reply to his objections under the following heads: — (1.) The
mode of occurrence of Prototaxites. (2.) Its microscopic struc-
ture. (8.) Its probable affinities.

1. MinJe of Occurrence. — This alone should suffice to convince

kany practical palaoontologi.st that the plant cannot be a sea-weed.
Its large dimensions, one specimen found at Gaspe Buy being
three feet in diameter ; its sending forth strong lateral branches,
and gnarled roots ; its occurence with land pl<*nt8 in beds where
I -- there are no marine organisms, and which must have been de-
posited in water too shallow to render possible the existence of
the large oceanic Algae to which Mr. Carruthers likens the plant.
These a. a all conditions requiring us to suppose that the plant
grew on the land. Further, the trunks are preserved in sand-

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stone, retaining their rotundity of fbrm even when prostrate; and
are thoroughly penolrutcd with silica except the thin coaly bark.
Not only are Algae incapable of occurring in this way, but even
the less dense and durable land plants, as Sigillaria3 and Lepi-
dodendra are never found thus preserved. Only the extremely
durable trunks of coniferous trees are capable of preservation
under such circumstances. In the very beds in which these oc-
cur, Lcpidodendra , tree ferns and Fs'dopliyton, are flattened into
mere coaly films. This absolutely proves, to any one having ex-
perience in the mode of occurrence of fossil plants, that here we
have to deal with a strong and durable woody plant.

These considerations were dwelt on in my published descrip.
tions of Prototaxites, but they naturally have more weight in my
judgment than in that of Mr. Carruthers. Geologists and palae-
ontologists will appreciate them.

2. Microscojnc Structure. — It would be tedious to go into the
numerous scarcely relevant points which Mr. Carruthers raises on
this subject. I may say in general that his errors arise from
neglect to observe that he has to deal not with a recent but a fos-
sil wood, that this wood belongs to a time when very generalized
and humble types of gymnospcrms existed, and that the afl&nities
of the plant are to be sought with Taxincae, and especially with
fossil Taxineae, rather than with ordinary pines.

Mr. C, after describing Prototaxites according to his own
views of its structure, expresses the opinion that '* the merest
tyro in histological botany " may see that the plant could not be
phaenogamous. But if the said tyro will take the trouble to refer
to the beautiful memoir on the Devonian of Thuringia, by Richter
and Unger,* and to study the figures and descriptions of Apor
oxylon primigenium^f Stigmaria annidari8,Calamopterts debilis,
and Calamosyrinx Devonicus, he will find that there are Devonian
plants referred by those eminent palaeontologists to Gymnosperms
aod higher Cryptogams, which fall as far short of Mr. Carruthers'
standard as Prototaxites itself Nothing can be more fallacious
in fossil botany than comparisons which overlook the structures
of those primitive palaeozoic trees which in so many interesting
Ways connect our modern gymnosperms with the cryptogams.

•■Trans., Vienna Academy, 1856.

t I have elsewhere compared Aporoxylon with Prototaxites, ' Jour,
Oeol. Soc' 1862, p. 306. Report on Devonian plants.

^■\cji^

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It is scarcely necessary to reply to such a statement as thnt
the fibres of Prototaxites have no visible terminations. They
are very long, no doubt, and both in this and their lax coherence
they conform to the type of the yews. In Mesozoic specimens of
Taxoxyhn which I have now before me, the fibres are nearly as
loosly attached and as round in cross section as in Prototaxites.
In these, as in Prototaxites, water-soakage has contributed to
make the naturally lax and tough yew-structure less compact, and
to produce that appearance of thickness of the walls of the fibres
which is so common in fossil woods.

Disks or bordered pores in Prototaxites I did not insist on,
the appearance being somewhat obscure; but Mr. Carruthers
need not taunt me with uffirniing the existence of such pores in
the walls of cells not in contact. Pores, if not bordered pores,
may exist on such cells, and the wood cells of Prototaxites are in
contact in many places, as may easily be seen, and even where
they appear separate, this separation may be an effect of partial
decay of the tissues.

Mr. Carruthers converts the spiral fibres lininj^ the cells of
Prototaxites into tubes connecting the cells. This is a question
of fact and vision, and I can only say that to me they appear to
be solid, highly refracting fibres; and under high powers, pre-
cisely similar to those of fossil specimens of Taxoxylon from
British Columbia, and to those seen in charred slices of modern
yews. I may further say that Mr. Carruthers' figure (Plate
XXXII.) is in my judgment to a great extent imaginary.

But what of the arrangement of these fibres. It is true that,
as I have stated, they appear in some cases to pass from cell tp
cell, and I hesitated to account for this appearance. Mr. C.
might, however, have spared himself the remark that " if Dr.
Dawson knew anything whatever about a vegetable cell, and the
formation of the spiral fibre in its interior, he would not have
written such nonsense" — (a specimen, by the way, of the ameni-
ties of British Museum Science, as represented by Mr. C.)
The possibilities of such an appearance, as yet, perhaps, unknown
in the plant-rooms of the Museum, result from the following con-
siderations: (1.) In more or less crushed fossil plants, it is not
unusual to see what are really internal structures appearing to
pass beyond the limits of the cell-wall, from the mere overlapping
of cells. I have good examples in the Mesozoic Taxoxylon
already mentioned. (2.) In fossil woods the original cell-wall is

often entirely destroyed, and only the ligneous lining remains,
perhapsi thickened by iticrustation of mineral matter within. In
this case the original lining of the cell may seem to be an exter-
nal structure. 1 have examples both in Mesozoic conifers and in
carboniferous plants. Long soaking in water and decay have
thus often made what miy have been a lining of wood-cells appear
as an intercellular matter, or an external thickening of the walls.
(3.) In decayed woods the mycelium ol' fungi often wanders
through the tif^sues in a matuier very perplexing; and I suspect,
though I cannot be certain of this, that some fossil woods have
been disorganized in this way. At the time when my descrip-
tion was published, I felt uncertain to which of these causes to
attribute the peculiar appearance of Prototaxites. I have now,
from >«ub.Ne<jueiit study of the cretaceous Taxineoc of British
Columbia, ■-!= little hesitation in adopting the first and second ex-
planations, or one of them, as probable.

Mr. Carruthers does not believe in the medullary rays of Proto-
taxites. The evidence of these is the occurrence of regular lenti-
cular spaces in the tangential section, which appear as radiating
lines in the transverse section. The tissues have perished ; but
some tissues must have occupied these spaces; and in fossil woods
the medullary rays have often been removed by decay, as one
sometimes sees to be the case with modern woods in a partially
decayed state. Mr. Carruthers should have been more cautious
in this matter, after his rash denial, on similar grounds, of me-
dullary rays in Sigillaria and Stigmaria, contrary to the testimony
of Brongniart, Goeppert, and the writer, and the recent exposure
of his error by Professor Williamson. That the wood-cells have
been in part crushed into the spaces left by the medullary rays
is only a natural conse(iucnce of decay. The fact that the me-
dullary rays have decayed, leaving the "vood so well preserved,
is a strong evidence for the^durability of the latter. The approval
with which Mr. C. quotes from Mr, Archer, of Dublin, the naive
statement that " the appearance of medullary rays was probably
produced by accidental cracks or fissures," would almost seem to
imply that neither gentlemen is aware that radiating fis.sures in
decaying exogenous woods are a consequence of the existence of

• lleport of Geol. Survey of Canada, now in course of publication.
The collections contain wood showing the structure of yew, cypress,
oak, bfrch, and poplar, all from rocks of cretaceous age.

medullary rays, [or that water-soaked wood caiiDOt be cracked in
this way.]

Perhaps the grossest of all Mr. Carruthers' histological errors
is his affirming that Kiuie of my specimens of Prototaxites show
merely cellular structures, or are, as he .says, " made up of
spherical cells." Now, I affirm tliat in all my specimens the
distinct fibrous structure of Prototaxites occurs, but tluitin parts
of the larger trunks, as is usual with fossil woods, it has been re-
placed by concretionary structure, or by that pseudo cellular
structure which proceeds fr(»m the Ibrmation of granular crystals
of silica in the midst of the tissues. Incredible though it may
appear, I know it to be a fact, as all the specimens I gave to Mr.
Carruthers had been sliced and studied by myself, that it is this
crystalline structure which the botanist of the british Museum
mistakes for vegetable cells. ^'' I think it right to state here that
I not only gave Mr. C. specimens in these different states of pre-
servation, but that I explained to him their nature and origin.

It is unnecessary to follow further the histological part of the
question, as my object is not so much to expose the errors of Mr.
Carruthers as to illustrate the true structure of Prototaxites.

3. Ajfuilties. — In discussing these I must repeat that we must
bear in mind with what we have to deal. It is not a modern
plant, but a contemporary of that "prototype of gymnosperms ''
Aporoxylon, and similar plants of the Devonian. Further, the
comparison should be not with exogens in general, or conifers in
general, but with Taxineau, and especially with the more ancient
types of these. Still further, it must be made with such wood
partly altered by water-soMkage and decay and fossilized. These
necessary preliminaries to the question appear to have been alto-
gether overlooked by Mr. Carruthers.

3Iy original determination of the probable affinities of Proto-
taxites, as a very elementary type of taxine tree, was based on
the habit of growth of the plant — its fibrous structure, its spirally-
lined fibres, its medullary rays, its rings of growth, and its coaly
bark, along with the durable character of its wood, and its
mode of occurrence ; and I made reference for comparison to
other Devonian woods and to fossil taxine-trees.

" In fossil-woods, the carbonaceous matter, licing ncKiccd to a
puipy mass, Rometimes partly becomes raouklcd on the surfaces of
hexagonal or granular crystals, in such a manner as to deceive very
re idily an observer not aware of this circumstance.

il

Mr. Gar.uthcrs prefers to compare the plant as to stmcture
with cer'.aiD chlorospermous Algae, and us to size with certain
gigantic Melanospcrms, not pretended to show similar structure.
This is obviously a not very scientific way of establishing affini-
ties. But let us take his grounds sep.irately. He selects the
little jointed calcareous sea-weed ILilimcdii opuntia, as an
allied structure, and copies from Kutzing a scarcely accurate
figure of the tissue of the plant as seen after the removal of its
calcareous matter.* He further gives u defective description of
this structure; whether taken from his own observation or from
Kutzing, ho does not say. Harvey's description, which I verified
several years ago, in an extensive series of examinations of these cal-
careous Alg«3, undertaken in consoquenceof a suggestion that Eo-
zocin might have been an organism of this nature, is as follows: —
" Aftur the c ilc ircous matter of tlie frond has been removed by acid
a spongy vegetable structure remains made up of a plexus of slender
longitudinal unicellular filaments constricted at intervals, and at
the constrictions emitting a pair of opposite decompound, dicho-
tomous, corymboso-fustigiate horizontal ramelli, whose apices co-
here and form a thin epidermal or peripheric stratum of cells."
It will be seen at once that this structure has no resemblance
whatever to anything existing in Prototaxites, even as interpreted
by Mr. C, and without taking into account the fact that Hall-
vicdn opuntia is a small calcareous sea-weed, divided into flat
reniform articulations, to which this structure is obviously suited^
as it would be equally obviously unsuited to the requirements of
a thick cylindrical trunk, not coated with calcareous matter.

In point of size, on the other hand, Mr. Carruthers adduces
the great Lcssonia of the Antarctic seas, whose structure, how-
ever, is not pretended to resemble that of Prototaxites except in
the vague statement of a pseudo-exogenous growth. Lcssonia I
have not examined, but the horny Lamuuiria' of our North
American seas have no resemblance in structure to Prototaxites.

Nothing further, I think, need be said in reply to Mr. Car-
ruthers' objections; and Ncmatophj/cus may be allowed to take
its place along with a multitude of obsolete fucoids which strew
.he path of palaeontology. As to Prototaxites, it is confessedly
an obscure and mysterious form, whose affinities are to be dis-

• A more characteristic figure is given in Harvey's "Nortli Ameri-
can Algaj."

cusHcd with caution, and with a due consideration of its venerable
age and state of preservation, and probably great divergence from
any of our modern plants; and it is to be hoptd that ere long
other parts than its trunk may be discovered to throw light on
its nature. Until that takes place, the above remarks will be
sufficient to define my position in regard to it; and I shall decline
any further controversy on the subject until the progress of dis-
covery reveals the I'oliage or the fruit of this ancient tree, belong-
ing to a type which I believe passed away before even the Car-
boniferous flora came into existence.