Palaeont
L

Lesquereux, Leo

On fucoides in the coal
formations.

I

fc*

ON FUCOIDES IN THE COAL FORMATIONS

by

Leo Lesquereux

^6& 3?T4 3S

.

Trans A P S. Vol. XIII. Plate VII.

l,o» Lesquereui, del

T. Sinclair's litlijhil1

ARTICLE X.

ON FUaOIDES IN THE COAL F 0 RM A T 10 N S.*— [W it h a Plate.]

BY LEO LESQUEREUX.

Bead May 18th, 1866.

§1. DISCOVERY OF FUCOIDES IN THE COAL MEASURES OF SCIENTIFIC IMPORTANCE.

The scarcity of Fucoidal remains in the strata of the true Coal Measures is so re-
markable that it is questionable whether any species of true marine Algae has hereto-
fore been described from these formations. Up to 1836 one specimen of Fucoides only is
mentioned in Thompson's Outlines of Mineralogy, Geology, and Mineral Analysis, at the
end of a catalogue of fossil plants of the Coal Measures, containing 290 species, under
37 genera.-}- Since that time, none of the palaeontologists who have enumerated or de-
scribed coal plants, have noticed a single species of Fucoides from the Carboniferous
formations, either of Europe or of America, except the doubtful forms which I have
noticed in a former paper.J Considered in itself, therefore, the discovery of true Fucoidal
remains in strata ascertained to belong to the Coal Measures, is a subject of some scien-
tific interest. This fact, moreover, is intimately connected with the question of the dis-
tribution of Fucoidal remains in formations of different ages, and of their value and sig-
nificance for the identification of the strata where they are found. It bears also upon the
problem of the economy of marine Algae in nature: that is, of the amount and worth
of the materials which they have brought and still bring to the economizing forces of
this omnipotent treasurer. Viewed under these various aspects, the subject may be con-
sidered indeed of some scientific importance.

$2. HABITAT OF THE FUCOIDES HERE EXAMINED.

The habitat or the position occupied by the plants described here, is somewhat peculiar.
They were found attached or flattened on the lower surface of a thin stratum of limestone,
immediately overlaying a bed of coal six to eighteen inches thick. The Fucoides, for they
belong evidently to a kind of marine plants, have thus grown, either as a part of the ma-

* In these remarks, the term Fucoides is used in its general sense, as representing remains of evidently marine
plants, or Algae, whose relation to living species is obscure or not yet fully ascertained.

f Quoted by J. P. Lesley, Manual of Coal, p. 219. f

I Sillimsin's Journal (2), vol. xxxii, p. 194. ftj

•o ,

0

VOL. XIII. — 40 -\ / ^

314 FUCOIDES IN THE COAL FORMATIONS.

terials of which the coal is a compound, or immediately over them. For they appear to
derive the black color, which seemingly paints them on the limestone, rather from the
coal than from their own substance. When some detached blocks of the limestone have
fallen into the creek, and, washed for a time, have been cleared of the coal which adheres
to the lower surface, the matter becomes bleached, and the remains "of Fucoides appear in
slightly depressed and dark distinct outlines. But when the coal, which adheres to the
limestone as if it was strongly glued to it, is removed by mechanical force, the stone
preserves its black color, and the remains of these plants are scarcely discernible. On
the line of contact with the coal and for one or two inches above it, the limestone, whose
thickness varies from twelve to eighteen inches, is somewhat shaly, though of a piece, and
homogeneous. It is a kind of black band, containing sulphur and iron in large propor-
tions, and essentially composed of broken remains of innumerable marine shells. Though
hard, compact, and in banks generally continuous, it breaks into large cuboidal pieces.
The Fucoides, which occupy only a few inches of the lower and shaly part of this lime-
stone, are mixed with the remains of shells, and often perforated and lacerated by them.

§3. NAME AND DESCRIPTION OF THE PLANTS.

Caulerpiies marginatum, spec, nov., is the name of these Fucoidal remains. Their form,
however variable,* may be compared to that of a lyre or harp. From a horizontal base,
the margins, at first nearly parallel, slightly diverge in ascending, and then unite into a
rounded top, as in fig. 2. Or the outer margin, diverging more in ascending from the
base, becomes more extended than the other, and is once or twice broadly lobed or only
wavy, as in fig. 3. The fronds vary in length from two inches to one foot, are half as
broad as long, and surrounded by an apparently fleshy or tubular margin from one-eighth
to one-fourth of an inch broad. Strongly arched ribs, apparently produced by alternate
inflation and thinning of substance, pass from the inner side of the rim to the other
border, filling the whole lamina. These arched lines look somewhat like the forking or
dichotomous thickened veins of some Gyclopteris of the coal. But they are not true
nerves, for they do not regularly branch or connect with each other. They abruptly vary
in thickness or change their general direction, even crossing each other in various ways.
This last appearance is likely caused by compression of a body somewhat inflated like a
bladder. The ribs, thin and narrow at and near the margin of the frond, are enlarged in
the middle. They seem to be produced by such a spongy network of anastomosing fila-
ments, as is seen in some of our living Algae, which serves especially to strengthen the
structure of the plants. The base of the fronds, abruptly and nearly horizontally cut, is
joined at one of its corners, generally more acute than the other, to a stalk or stipe, per-

* See plate 1.

FUCOIDES IN THE COAL FORMATIONS. 315

haps a primary stem (surculus), which is either linear, elongated, apparently tubular,
connecting the frond with some point of attachment, or a short, inflated, oval, bladdery
tubercle, resembling an organ of suspension in water. These stipes vary in thickness
from one-fourth to one-half of an inch, are very abundant on the limestone, much more
so than the fronds, appearing like flat cylindrical pipes, mostly simple, curved in many
ways, and generally somewhat inflated at one end. I have copied fig. 7 of plateWf as it
is seen on the stone. It seems to represent a branching stipe. But this is probably a
deceptive appearance, caused by a casual superposition and compression of three different
parts of simple stalks. ,

H- RELATION OF THESE FUCOIDES TO OTHER SPECIES OF THE PALEOZOIC AGES.

These Fucoidal remains so remarkably resemble some of those figured by Mr. Vanuxem,
in his Geological Report of New York, under the general name of Fucoides Cauda-galli,
Fucoides velum, &c, that their close relation cannot be denied. Specimens of our species,
when the rim has been casually destroyed, are exactly like fig. 2, p. 128, of Vanuxem 's
Fucoides Cauda-galli. Indeed, except the border, it would be impossible to point out any
character which might serve to specifically distinguish them.

In a re-examination of these fossil plants, the celebrated palaeontologist, Prof. James
Hall,* considers the circular form of the frond of Fucoides Cauda-galli as a result from its
development around an ascending spiral axis, the frond expanding more and more in as-
cending. In consideration of this peculiar mode of growth, the author has grouped the
plants of this kind into a new genus, Spirophyton, in which he enumerates four species '
S. Cauda-galli, S. velum, both old species of Vanuxem, and S. typum and S. crassum,
two new species.

Though the very clear descriptions and good figures given by Prof. Hall seem indeed to
indicate, at least for his new species, the growth of a frond around a spiral axis, it is plain
also that we cannot suppose for the plant here above described a similar mode of develop-
ment. The same can be said, I think, of both the forms represented in Prof. Hall's report,
the one p. 80, fig. 2, which the author considers as a distorted portion of a last volution of
a spiral of Spirophyton Cauda-galli ; and the other, p. 81, fig. 3, named S. velum. For
the first of these fronds has, as it has been remarked, exactly the same general form and
appearance as the plant represented fig. 2 of our plate, and the other bears at one of its
corners the broken remains of what is rightly called a stem by M. Vanuxem, which
indicates a mode of growth similar to that of our Caulerpites marginatum. Therefore,
these closely related three forms should be forcibly ejected from the genus Spirophyton,
this name being inapplicable to plants whose growth has been as a plain untorted lamina.

The way of reconciling these discrepancies is, I think, to admit that the fronds of this

* Seventh Annual Report of the Regents of the University of New York, Appendix D, pp. 76 to 84.

316 FUCOIDES IN THE COAL FORMATIONS.

group may casually, under peculiar circumstances of habitat, have their laminas or fronds
contorted or twisted around their axis, which is here merely lateral. This twisting occurs
in a remarkable degree in many species of our living Algae, especially in those of a hard
leathery texture. The most common Fucus vesiculo&us, for example, can be seen around
Boston, on grassy meadows submerged at high water, with its fronds so strongly twisted
that its length is reduced by one-half, and that it then looks rather like a whorl of leaves
surrounding a central axis than like a long flat linear frond, which it is really. If, there-
fore, fronds, like the one represented p. 80, fig. 2, of Prof. Hall's report, or plate 1, fig. 2,
of ours, whose length attains one foot, were twisted around a lateral axis, here the con-
tinuation only of the primary stem, which may force the torsion, the figure resulting from
a cross-section of any part of the twisted frond, or from its perpendicular compression,
would represent a disk just like that of the new species of Spirophyton. And the same
twisted leaves, if compressed in different ways and at various angles, would of course pro-
duce multiple deformations like those remarked in the polymorphous Fucoides Cauda-
galli. If this supposition is right, and if all the forms under which the Fucoides of this
group are seen, may be explained by it, it excludes the necessity of a new genus and pre-
vents the scattering of plants of similar characters into different groups.

§5. RELATION OF THESE FUCOIDES TO LIVING ALGJ5.

It is right to remark, nevertheless, that we have now a genus of living Alga?, repre-
sented by one known species only, whose growth seems to be somewhat analogous to the
spiral development of the Spirophyton, as it is described by Prof. Hall. It is the Thalas-
siophyllum clatlirtis, Post and Pup., growing on the northern shores of the Pacific, in Rus-
sian America. According to Mertens, who has described it, the stipe of this plant is very
bushy and branching, each branch bearing at its extremity a leaf, which unfolds spirally
in such a manner that a spiral border, wound round the stipes, indicates the growth of the
frond. This frond presents a large convex bent lamina without nerves, or, to a certain de-
gree, a leaf, of which one-half is wanting, for the stipe may be considered as an eccentric
nerve.* Though an analogy of development may, from this description, appear to exist
between the fossil and these living Alga?, there is, I think, an evident and great difference.
In Spirophyton, as it is described and figured, it is not a kind of border or stalk, which
causes by its own twisting the bend of the frond ; it is the lamina which unfolds itself in
spiral from its point of attachment and expands in ascending. Hence, fronds of this kind
can be but simple, while the Northern Alga? of the Pacific are remarkably bushy branch-
ing. These, moreover, belong to a class of highly organized Alga?, while in early geo-
logical ages and from analogy with what we know of other beings, we can look in the
vegetable world for types only of a very simple organization.

* T. H. Harvey's Nereis Boreali Americana, vol. i, p. 97.

FUCOIDES IN THE COAL FORMATIONS. 317

This simplicity of structure, with some peculiar characters of the Fucoidal remains
under examination, seem to fix their relation with the Gaulerpce, a group of Chlorosperm
Algae of our time. " The fronds of these plants consist of prostrate primary stems {surculi),
rooting from their lower surface and throwing up erect branches or secondary fronds of
various shapes. Their substance is horny, membranaceous, destitute of calcareous matter,
their structure uncellular, the cell (or frond) continuous, strengthened internally by a
spongy network of anastomosing filaments, and filled with a semi-fluid grumous matter."*
The primary fronds or stalks of the species of this order are smooth and glossy, a charac-
ter particularly marked in Caulerpites marginatus of ours. For, on the limestone, even
when it has not been washed by the water of the creek, these stalks of a dull grayish color
are clearly defined, perfectly smooth, even shining or polished. The development of the
secondary fronds of the Caulerpae is multiform in the extreme, as can be expected in a plant
which is of the simplest structure and is formed by the continuous development of a single
cell, or is, so to say, nothing but a kind of bag of a flexible tissue. In Gaulerpa prolifera,
Lam., the secondary frond expands into a tongue-shaped, flat petioled, leaf-like division,
which is itself proliferous from any part of its surface. In other species the secondary
fronds are sometimes pinnately branching into elongated bladdery cylindrical appendages,
sometimes irregularly divided into ribbon-like branches, without any appearance of order.
Even in Caulerpa clavifera, Ag., these secondary fronds are more or less densely set all
around by scattered club- or top-shaped vesicular branchlets. The only character which
renders our fossil plant in some way different from the forms which we are accustomed to
find in this group of Alga?, is its eccentrical shape. But it is seen from plateVEJfig. 4, that
the secondary frond is not a second frond, implanted on or born from the primary one, but is
really a mere continuation by inflation of the stalk. This, expanding like a bladder, is
forced upwards, the division of the stalk forming the thickened or smooth border around
it. The stalks or surculi, as seen in figs. 5 and 6, are inflated in various ways, and may,
even after dilating into laminas, take again their tubular, more simple form, a disposition
which is seen also in some species of Cuulerpce.

It is in consideration of those natural affinities, that I have placed the new species of
Fucoides of the coal in the genus Caulerpites of Sternberg ; and the same reasons would
induce me to admit into it all the related forms described by Prof. Hall under the name of
Spirophyton, as well as the peculiar Fucoides Serra described by Brongniart.t This last,
according to the remarks of that celebrated author, was found in the limestone of Transi-

* Nereis Boreali Americana, by T. H. Harvey, vol. iii, p. 12. Most of the remarks concerning the Caulerpae
are taken from this admirable work.

f Vegetaux Fossiles, p. 71, tab. G, figs. 7 and 8.

318 FUC01DES IN THE COAL FORMATIONS.

tion at Point Levy, near Quebec, Canada. Its likeness to our species is rather in the
mode of growth than in the form. It has nevertheless an eccentrical expansion of the
secondary frond, from a round, linear, apparently tubular stalk, which is sometimes only a
bladdery oval tubercle. The fronds themselves, though narrower, deeply dentate on one
side, and without arched ribs, have the same general outline as Canlerpites marginatus.
Indeed, in comparing the upper part of fig. 7 of Brongniart with fig. 6 of our plate, or fig.
8 of Brongniart with our fig. 2, one can but see that these so nearly allied forms are of a
same type, and can but be admitted in the same genus.*

§6. GEOLOGICAL HORIZON OF THE LIMESTONE MARKED WITH REMAINS OF CAULER-
PITES MARGINATTJS.

The new species of Caulerpites was found on Slippery Rock Creek, opposite Wurtem-
berg, Lawrence County, Pennsylvania, at the base of a hill about three hundred and fifty
feet high, abruptly cut down by the erosion of the creek. The succession of the strata
thus open to view is seen in the following order, ascending :

1st. At the low-water level of the river, a bed of soft, black, easily disaggregated shales,
intermixed with small oval pebbles of carbonate of iron. At its upper part, the shales
pass into a kind of yellowish ball or clay iron ore, their whole thickness varying from five
to eight feet here around.f

2d. They are overlaid by a bed of bituminous, hard splint coal, sometimes shaly, five
to twelve inches thick, rarely more, covered by the limestone, with Fucoidal remains, as
it has been described above. At Wurtemberg this limestone is one foot thick. In as-
cending the creek to about five miles above this place, it continues in view at the base of
the hills wherever they are cut by erosion. It preserves the same horizon, is marked by
the same species of plants, and its greatest thickness is not over eighteen inches.

3d. Over the limestone, fifteen feet of soft, grayish shales, without any trace of remains
of fossil plants.

4th. A bed of sandstone, five feet thick, passing sometimes to a hard compound of
coarse-grained fire-clay, with leaves and stems of Stigmaria.

5th. Two feet fire-clay.

6th. Three feet hard black limestone, of the same appearance and compound as the
limestone of the Fucoides, but without remains of plants.

7th. A succession of thick strata of shales, cut by thin beds of Stigmaria fire-clay and
shaly sandstone, with streaks of coal. The shales have an average thickness of one

* Prof. Brongniart (loc. cit.) compares his fossil plant to some species of Amansice, especially to Aviansiu
semijnnnala. Prof. UDger, in his Genera and Species, places it in the genus Sphcerococcites of Sternberg.

f At some other places, on Beaver River for example, these shales attain a thickness of twenty feet, being
cut or underlaid by one or two beds of coal, as in Kentucky.

FUCOIDES IN THE COAL FORMATIONS. 319

hundred and fifty feet, while the intermediate strata do not have altogether a thickness of
twenty-five feet. The shales are generally soft, slightly micaceous, and black-spotted by
oxide of iron. They contain in places a quantity of branching cylindrical Fucoides,
mostly resembling the small variety of what has been called PaJceophycus tubularis by
Prof. J. Hall*

8th. These shales are still overlaid by a thick bank of hard, gritty, micaceous sandstone,
generally conglomerate at its upper part, and capping the hills here around. Its lower
part, somewhat shaly, is also marked by abundant Fucoidal prints. I say prints, because
these Fucoides in the sandstone are not true remains of plants, but only the moulds left
by the decay of marine Algae, whose place has been filled by a softer whitish sand. Ac-
cordingly, the original formjof the plants are pretty distinctly printed on the stone. The
moulds are generally placed horizontally on the stones, but sometimes penetrate them
obliquely or even vertically. These Fucoides are somewhat thicker than those of the
shales, varying in thickness from one-half to one inch, either simple, like flexuous pipes,
or irregularly forking on one side only, or dividing from a central axis, and sending
branches in every direction. They have, as much at least as can be seen from these
moulds, the same form and size as the large variety of PaJceophycus tubularis, Hall, as it
is represented figs. 1 and 2, quoted above.

Though the shales of this section are mostly soft, grayish, apparently well fitted for the
preservation of remains of coal plants, there is not, in the whole, any trace of ferns or of
any of the species of land plants generally and commonly found in the Carboniferous
measures. At one place only, just below the mill, one mile above Wurtemberg, the bed
of coal at the base of the section is divided into two members by a shaly sandstone, which
bears the prints of the bark of Calamites, Lepidodendron, and Sigillaria. The upper
division of the coal is here still overlaid by the limestone with Gaulerpites margiaatus.

This distribution of strata strikingly resemble what is seen in some part of the Subcar-
boniferous measures of Kentucky, Illinois, and Arkansas, where the upper and even the
second bed of the Archimedes Limestone are underlaid by shaly sandstone, marked with
remains of large coal plants, especially trees and thin strata of coal. In the same way
the fossil remains covering the soft shales and printed with the upper Conglomerate Sand-
stone, are like those remarked in the Chemung, along Oil Creek, or in the Waverly Sand-
stone of Ohio. They appear indeed identical. Relying then on paloeontological evidence,
I could but consider the hill opposite Wurtemberg as formed mostly of Chemung measures,
and the Conglomerate Sandstone of the top as the equivalent of the Millstone grit. It
was only after conferring upon the matter with my friend, Prof. J. P. Lesley, than whom no

* Palaeontology of New York, vol. i, p. 7, tab. 2, figs. 1, 2, 4, 5.

320 FUCOIDES IN THE COAL FORMATIONS.

geologist is better acquainted with the distribution of the measures in the whole extent of
Pennsylvania, that considering the anomaly of the presence of the Chemung in that part
of the State, I began a stratigraphical survey of that country, disregarding every kind of
palaxmtological evidence.

Beginning at Homewood Station in Beaver County, the Millstone grit is there exposed
along Beaver River with a thickness of one hundred and sixty feet, its base resting on a bed
of ball and clay iron ore, soft black shales, with pebbles of carbonate of iron, thin layers
of coal, &c. Higher up, at Homewood Furnace, and at the mouth of Coneconessing Creek,
the Millstone grit is still one hundred and ten feet thick, and is underlaid by the same kind
of shales and ball iron ore. Up the Coneconessing the stream flows between banks of the
Millstone grit, which slowly decreases in thickness. At the mouth of Smalley's Run, six miles
above, these measures are only sixty feet thick, and the Subcarboniferous strata exposed
there show the same nature and distribution as at Homewood Station. The thinning con-
tinues at about the same rate to the mouth of Slippery Rock Creek, where banks of hard
Conglomerate, forty feet thick, descend to nearly the level of the river. Six to eight feet
of Subcarboniferous measures are exposed here at low water. From here, in ascending
Slippery Rock Creek, the decrease in the thickness of the Millstone grit becomes more
rapid and irregular ; these strata changing here and there into shaly sandstone, five to six
feet thick, then disappearing entirely, to be seen in place again a little higher up in the
creek. The last appearance of the Millstone grit is just below the lower mill at Wurtem-
berg, where the sandstone, still hard and gritty, is six feet thick, and the black shales and
clay iron ore are exposed under it six to eight feet thick ; there it definitely loses itself
in a thin bed of soft shaly sandstone, wedging into the top of that clay iron ore which in
the section is marked as under the bed of coal. From Wurtemberg these strata, preserving
the same character •and horizon, continue along the creek, without any trace of sandstone,
to six miles above, where the Millstone grit reappears in the same manner and at the same
horizon as it is seen passing away at Wurtemberg, and rapidly increasing in thickness.
At Seceder's Bridge, nine miles above Wurtemberg, it is already one hundred and ten feet
thick, underlaid by forty-nine feet of Subcarboniferous measures.

From these observations it follows :

1st. That the whole thickness of the strata marked in the section of the hill opposite
Wurtemberg, including the lower bed of coal and the limestone with Fucoidal remains
{(Juulerpites marginatus), belongs to the Carboniferous formations.

2d. That, from Homewood Station to Seceder's Bridge, a distance which, in a straight
line, is not more than fifteen miles, there is in the Millstone grit formation a wide, nearly
abrupt gap, about five miles broad, where the Carboniferous measures, immediately over-
laying the shales of the Subcarboniferous, are mostly marked with remains of marine

FUCOIDES IN THE COAL FORMATION'S. 321

plants of the same type, if not of the same kind, as those which we generally consider as
characterizing the Chemung group.

$7. GENERAL DISTRIBUTION OP SOME SPECIES OF FTjl?OIDES IN THE PALEOZOIC
AGES AND THEIR VALUE AS CHARACTERS OF SYNCHRONISM.

The moulds of Fucoidal plants, observed in abundance at the base of the gritty sand-
stone which caps the hills at and around Wurtemberg, about the height of three hundred
feet in the Coal Measures, represent a species apparently identical with, or at least undis-
tinguishable from the large variety of Palceophycus tubularis, Hall. The Fucoides in the
shales, inferior to this sandstone, resemble the small forms of the same species and Palceo-
phycus irregularis, Hall, which Prof. Goppert considers as a mere variety of it. Now, the
remains of marine plants of this kind already appear in the Lower Silurian Calciferous
sandstone, and may be considered as representing some of the primordial types of the veg-
etable world. The polymorphous Fucoides antiquus of the authors {Buthopteris antiquata,
B. gracilis, B. palmata, B. impudica, B. rarnosa, Hall) is common in strata of the Upper
Silurian Clinton group ; is especially abundant in the Chemung of Pennsylvania and
Ohio, and reappears in the Cretaceous formations of Europe. At least Fucoides Targioni,
Brgt., of this epoch, so well resembles in its multiple varieties the different forms of F.
antiquus, that it cannot be separated by appreciable characters.* The group of Fucoides,
which we have examined in this paper, has representative fossil remains, apparently iden-
tical in species, in the whole extent of the Devonian Measures. At least the same form of
Fucoides Cauda-galli of the Corniferous period is seen in the Chemung or Waverly sand-
stone of Ohio, and is especially abundant in strata scarcely fifty feet lower than the base
of the Millstone grit of Southeast Kentucky. It may be that the fossil remains represent
different species, for even Caulerpites marginatus, which ascends into the Coal Measures, is,
when its border is casually destroyed, undistinguishablc from Fucoides Cauda-galli* But
we are authorized from these facts and others of the same kind to conclude that most of
the marine Alga?, of which remains are found in the Palaeozoic strata, have had a wide
range of distribution. From this, it is contended, perhaps rightly, that they cannot be
considered as reliable guides in the determination of geological horizons.

If this discredit was limited to the remains of marine Algae only, it would perhaps not
be worth considering in any way. But it touches, by inference, every kind of fossil
plants, and thus tends to eliminate as useless some palaeontological data which are cer-
tainly of practical importance. I allude to the remains of land plants, especially the coal
plants, some of which may be justly considered as characteristic even of the horizons of
the various beds of coal.

* Geological Report of Pennsylvania, p. 848. Goppert, Fossil Flora des Silurisehen, p. 434.

VOL. XIII. 41

322 FUCOIDES IN THE COAL FORMATIONS.

We know little indeed of the true forms and nature of fossil Hydrophites. Mere
cellular plants as they were, nothing of them has been preserved by fossilization but some
moulds or indistinct impressions ; hence the impossibility of discovering peculiar forms of
organism, which might be used as reliable specific characters. In looking over the innu-
merable remains of Fucoides, which cover some strata of the Chemung of Pennsylvania
or of the Waverly sandstone of Ohio, for example, we perceive at first such differences in
the shape of these fossils that their .separation into groups appears an easy task. But in
time, when these remains are more thoroughly studied, the gaps are filled by so many
intermediate forms that the whole fields of this vegetation of old appears like a grass-plot,
each blade of which has some peculiar feature, but none marked enough to make it posi-
tively distinct. Therefore we are led to admit, either that there are nearly as many spe-
cies as individuals, or only one species, represented by a great number of closely allied
varieties. Of course the impossibility of separating these fossil remains into well-charac-
terized groups renders them unavailable as geological guides.

This difficulty is not met with in the study of the fossil coal plants. For, like the acro-
genous vegetables of our time, a class to which they mostly belong, they have woody tissue
and vessels as constituents of their stems and foliage, and thus generally preserve their es-
sential forms, in the process of mineralization, at least under certain circumstances. The
leaves are not only well defined in outline, but their surface is generally marked by a dis-
tinct system of nervation, peculiar to most of the species. Some of these may be followed
and studied in the development of leaves, branches, trunks, and even fruits, the trunks
being recognizable by peculiar cicatrices on the bark, and the fructifications being some-
times found attached to the plants to which they belong. Hence, if the generic and specific
characters of these plants cannot be established on a true scientific basis, they are never-
theless evident enough to allow an identification of the remains found in connection with
the beds of coal, and thus to permit a reliable comparison in their distribution, or to fix the
peculiar horizon where groups of these plants may belong.

On the other hand, marine plants, like every other kind of vegetable, are apt to
modify their shape or to vary according to influences affecting the medium in which they
live. In the palaeozoic times the temperature of the sea was regulated rather by the heat
of the earth than by atmospheric action, and thus was scarcely variable. The same forms
of life could therefore be preserved in this medium for a great length of time, — longer
indeed in the vegetable than in the animal world, — for the life of plants is not in water
exposed to destructive accidents, like that of animals. And in its proceeding and re-

* Prof. James Hall, with remarkable foresight, obtained through his intimate acquaintance with the distribu-
tion of the Palaeozoic fossils, remarks in his report (loc. cit. p. 83) that species of Fucoides of the group of the
Cauda-yalli might perhaps be found in the Lower Coal Measures of Pennsylvania.

FUCOIDES IN THE COAL FORMATIONS. 323

ceding periods the sea brings with it and disseminates the seeds and branches of its Hy-
drophites, which germinate again, reproducing identical forms wherever circumstances are
favorable to their development. But that terrestrial plants, like those of which the coal is
a compound, should have been exposed to some modification of life after each of those
revolutions, which so often totally changed the surface of the land during the Car-
boniferous epoch, is an assertion which can only be considered reasonable. For each of
these revolutions may have influenced the atmosphere, either in its degree of density or
of humidity, or in its chemical compounds. Moreover, each of them at least has evidently
modified the land-stations inhabited by the plants, either by leaving the surface more or
less penetrated with humidity, or by covering it with deposits of another nature, or with
other elements of vegetation, sand, lime, mud, &c.

This assertion does not force us to the conclusion that all the plants of the Coal Measures
have been totally destroyed after each submersion of the land, and been replaced by other
species ; but only that some of the predominant species have lost in the number of their
representatives; that a few have disappeared, while new kinds have taken their place;
and that accordingly, for any particular horizon, the group of vegetation has a character
which may be recognized in its fossil remains, and serve as a true and reliable guide for
the identification of the coal strata.

This is not said as a reaffirmation of a personal opinion expressed elsewhere.* For, with
a few exceptions, all the authors who have studied the fossil plants of the coal, in relation
to their habitat, have come to the same conclusion. Prof. Brongniart's remarks on this
subject are worth recording. He says :f "But if the vegetation of our earth has been main-
tained without great changes during this whole period of time (the Carboniferous epoch),
it is not the less certain that very marked changes in the species may be observed during
the deposition of the various strata. Thus, in one and the same coal basin, each bed has
characteristic species which are not found in more ancient or more recent strata, and which
the miners themselves recognize as peculiar to a coal bed." Another celebrated European
palaeontologist and botanist, Prof. W. P. Schimper, of Strasbourg, records the same fact
in a recent work, saying^ that in the same coal basin a variation of species is observable
in passing from the inferior to the superior strata. So remarkable is this change that the
highest strata of the true Coal Measures are marked already by species which, like
Pterophyllum, are characteristic of the Trias, or even of the lower Jurassic formations.

Though the researches on the palseontological botany of our American coal fields are
only in an incipient state, and thus our acquaintance with the leading species of various

* American Journal of Sciences and Arts (2), vol. 30, p. 367, Geological Reports, &c.

f Tableau des Genres (1849), p. 95.

X Terrains de Transition des Vosges, Partie Palaoontologique (1862), p. 318.

324 FUCOIDES IN THE COAL FORMATIONS.

horizons is very limited, the value of what is known already and applied to the identifi-
cation of strata is demonstrated and strengthened by every new discovery.

$8. DOES PETROLEUM ORIGINATE FROM THE DECOMPOSITION OF MARINE PLANTS?

Considering the question of the origin of our deposits of petroleum, some geologists
have expressed the opinion that they might be due to the decomposition of marine plants,
as coal is the result of the decomposition of a terrestrial vegetation. This conclusion
is but natural, for there exists an evident correlation between the formation of both kinds
of deposits of bitumen. But this relation cannot be, or at least has not yet been, estab-
lished by direct proofs or experiments, and that is probably the cause why the subject has
not been studied more in detail.

$9. FECUNDITY OF THE MARINE VEGETATION AT THE PALEOZOIC AGES.

There is no doubt that the marine vegetation of the Palaeozoic ages can be compared,
for luxuriance, and in some measure for its composition also, to the terrestrial vegetation
of the coal epoch. From the Upper Devonian down to the Lower Silurian, some strata of
shales are not only covered, but indeed filled, sometimes for hundreds of feet in thickness,
with fossilized forms of Hydrophytes. These evidences of a primordial vegetable world
are far more numerous than the remains of land plants in the shales of the Coal Measures.
Nevertheless, they appear to belong to plants of a soft tissue, mere cellular, probably
mostly uncellular vegetables, the debris of which had not by much the same chances of
fossilization.

The superabundance of vegetation testified by fossil remains in Palaeozoic ages is in
accordance with one of nature's most evident laws. The amount of carbonic acid gas is
acknowledged to have been, at the Palaeozoic times, far greater in the atmosphere, and
also in the water of the seas, than it is now. The prodigious luxuriance of the vegetation
of the coal period is rightly ascribed to this fact. It cannot be supposed that in the sea
the vegetation, which is there also the intermediate agent between animal life and unor-
ganized bodies, gaseous or mineral, should have been in a diminutive state when its action
was the most in demand, like its development, for the purification of the water and the
transformation of the superfluous carbonic acid gas into organism and oxygen.

We have no proofs from fossil remains that the Hydrophytes of old attained a very
large size. The largest circular fronds of Fucoides Cauda-galli show a diameter of about
one foot ; the greatest length of the branching Fucoides in the Chemung is from two to
three feet. But we cannot judge all the vegetable representatives of an epoch from a
few fossilized specimens. These may have belonged to a species of a more compact organ-
ization, or to some kind of Corallines, which had their surface covered with a hard crust
of lime, while other groups of a soft, mere cellular tissue, which had representatives of
large size, have been totally decomposed and destroyed. There is no need however of this
hypothesis, on the size of the Palaeozoic Algae, to argue by comparison on the fecundity of

FUCOIDES IN THE COAL FORMATIONS. 325

the marine vegetation of old. Small species of Hydrophytes, in our time, afford sufficient
analogies. The great bank of Sargassum, which extends between the 20th and 45th
parallel of latitude, covers, according to Humboldt's computation, a space of more than
260,000 square miles. In places this floating bank is so thick as to arrest the progress of
vessels, and it appears at present to be of the same extent and to occupy the same place
as when it was first noticed by navigators. What can we then infer to have been the re-
sult of a vegetation whose force was at least double of what it is now, and which has
written its history in whole strata of great thickness!

§10. ANALOGY OF LIFE AND FUNCTIONS IN BOTH THE TERRESTRIAL AND THE MA-
RINE VEGETABLE WORLD.

It cannot be presumed that this whole vegetable world of Palaeozoic seas has left
nothing after it but useless petrified remains. In the march and development of nature's
productions, nothing of the materials employed is ever lost. The smallest atom of matter
is preserved in some way, if not constantly remodelled. Thus we find the key of a new
life, of a new creation, in the remains of a destroyed one. Thus, some leaves, preserved
by fossilization, in the shales of the Coal Measures, open to our view not only the whole
world of an ancient vegetation, but its predestinated result, coal deposits, slowly laid up
by its agency. Thus also the remains of marine plants, in the shales of the Devonian,
point out, I think, not only the fecundity of an ancient marine vegetation, but its result
in the contemporaneous deposits of petroleum. Indeed, both kinds of vegetation have
great analogy of life, if not of organism. The plants of the coal, by their structure, the
form of their long pointed leaves or indefinitely divided fronds, were shaped for the absorp-
tion and the transformation from the atmosphere of the greatest amount of carbonic acid
gas into woody tissue. The Chlorosperm of the Palaeozoic times, with their simple bladdery
conformation and their green color, were undoubtedly prepared to perform in the water
the same functions as the coal plants performed in the atmosphere. As the result of ter-
restrial vegetation has been, first woody tissue, and then, by its decomposition, coal, so the
result of marine vegetation has been, first cellular tissue, filled with a kind of liquid
carbon, and as the carbon is unalterable, the decomposition of the plant has left it free as
fluid bitumen or petroleum.

$11- WHAT CHEMISTRY INDICATES ON THE SUBJECT.

We cannot follow, in our day, by means of the accumulated remains of Hydrophytes,
the slow process of carbonization, and compare its results at different stages of its develop-
ment, as we can by help of the remains of land plants, in the formation of peat bogs, lig-
nites, &c. This only has been observed : When marine vegetables are thrown upon bogs
and mixed with terrestrial plants as compound of the peat, they do not leave any trace of
organism or primitive form, and the peaty matter, then of a deeper black color, is a softer,
more homogeneous compound, richer in bitumen. When, detached by storms or tides, Algas

326 F0COIDES IN THE COAL FORMATIONS.

are heaped in great masses on sandy shores, they promptly decompose, passing first to a
black, soft paste, and then to a glutinous fluid of the same color, which exhales a strong
disagreeable odor, and penetrates the sand. Chemistry has not analyzed these matters
resulting from the decomposition of Hydrophytes, nor even species of marine Algae ;* and
therefore it is not proved that there exists a direct relation between them and petroleum.
Chemistry demonstrates, however, that petroleum and coal are both compounds of the same
elements ; and the former matter being proved of vegetable origin, the second is neces-
sarily, by induction, referred to the same.f And as some substances, like iodine, which
was formerly procured from marine plants only, are now more abundantly obtained from
petroleum, chemical analyses, I think, confirm in that way the relation between petroleum
and Hydrophytes.

Though chemistry is not directly interested in it, it is but right to refer here to a pecu-
liar fact which bears upon the subject. The Alga?, especially the group of the Caulerpce,
feed some of the animals of the seas, remarkable for the size and the prodigious fatness of
their bodies. The green fat of the turtles, says Harvey,| so much prized by aldermanic
palates, may possibly be colored by the unctuous green juice of the Caulerpa;, on which
they browse. The same could be said of the color of the Devonian petroleum, which is
exactly that of the Chlorosperm Hydrophytes. It is not positively ascertained, I believe,
if whales and other marine mammifers of this kind, whose bodies are large reservoirs of
oily matter, are true Algas-feeders ; but when killed, the stomachs of these animals are
always found mostly filled with marine weeds.

4 12. GEOLOGICAL AND GEOGRAPHICAL DISTRIBUTION OF PETROLEUM DEPOSITS AND

FUCOIDAL REMAINS.

A last argument, no less conclusive on the subject, is taken from the geological and also
from the geographical relation between deposits of petroleum and Fucoidal remains.

Oil-bearing strata are seen in the Coal Measures mostly inferior to the big bed of coal
No. 1, which is often a cannel coal ; and sometimes also, but rarely, at a higher horizon, as,
for example, below coal No. 3, and also coal No. 12, generally in more or less evident con-
nection with cannel coal. This has probably led to the opinion, still admitted by some
geologists, that all the deposits of petroleum owe their origin to a slow decomposition of
coal, under some peculiar influences. As there has not heretofore been observed any indi-

* Prof. Liebig, to whom I wrote a rteumi of my opinion on the subject, with the request that he would point
out to me the result of chemical analysis of marine plants, if there were any, either in support or discredit of my
ideas, kindly answered : " That there were unhappily no analyses of species of Fucus, or of other Hydrophytes,
which could be used as affording support to my views. But that my arguments, based on exact researches, were
so conclusive, that for himself, at least, they had removed any doubt of the truth of the theory."

f See, on this subject, a very remarkable and most instructive paper, by Sterry Hunt, in the American Journal
of Science and Arts (2), pp. 156 to 171.

J Loc. cit., vol. i, p. 31.

FUCOIDES IN THE COAL FORMATIONS. 327

cations that remains of marine plants might have existed at some places mixed with the
aerial plants of the bogs of the coal epoch, it was not easy to account for such a phenom-
enon as that of the formation of coal and petroleum at the same horizon and under the
same circumstances. But this curious fact, I think, is explicable now. When the com-
bustible matter has been formed especially from the remains of aerial plants, whose tissue
was mostly vascular, or vascular and cellular, like that of the Lepidodendran, Sigtllaria,
ferns, etc., it becomes by mineralization a hard coal, with thin layers or distinct laminas,
sometimes shining, sometimes mixed with opaque layers and flakes of charcoal, and giving,
by combustion, a proportion of ashes according to the nature of the wood. When it has
been formed merely by floating fresh-water vegetables, like Stigmaria and its leaves, the
compound, originally half fluid and more easily decomposed, becomes, by the slow process
of combustion, compact, homogeneous, without apparent layers, tending to mere bitumen,
thus forming the different varieties of cannel coal. Now, I believe that when this floating
vegetation has been more or less densely intermixed with marine plants, and perhaps also
influenced by marine water, the almost total absence of woody fibres has casually prevented
the bedding of the material, and so, by slow maceration, part of it has been transformed
into fluid bitumen. It is probably for this reason that we see, sometimes, as at Brecken-
ridge, in Kentucky, a bed of cannel coal so nearly decomposed into petroleum that it can
scarcely be used as coal, and at a lower level, even in close proximity, and where every
trace of coal has disappeared, inferior strata of sandstone, strongly impregnated with
petroleum.

In descending from the base of the Coal Measures into the Devonian, we find deposits
of oil nearly in the whole thickness of this formation, with the exception of the old red
sandstone, equivalent of the Ponent and part of the Vespertine of Pennsylvania. All the
plants of this formation, and they are numerous enough, belong to swamp or land plants,
and no trace of petroleum has been seen in these measures. But down from this red
sandstone, the Chemung is full of remains of Fucoides, and where they are found all the
sandstone strata of this formation are more or less impregnated with oil.

Still lower the black shales of the Hamilton group are so much charged with bitumen
that they have often been considered as the true source of the Devonian petroleum. There
the remains are nearly, almost totally, obliterated. A few teeth of fishes and small shells,
very rarely large trunks of Lepidodendtwi, nothing more, at least in those extensive de-
posits, generally of great thickness, which border our Western coal basins. The color of
these shales, and the bitumen which they contain, indicate a formation under water, under
the influence of a powerful vegetation ; and a marine vegetation, without doubt ; else,
besides the well-preserved trunks of Lepidodendron, which have probably been brought
floating, we should find there other remains of aerial plants. At Worthington, in Ohio,

328 FUCOIDES IN THE COAL FORMATIONS.

whore I have spent much time in searching for fossil remains in these black shales, I have
seen them often covered with round spots of coaly matter, varying in diameter from half
an inch to one foot, showing no trace of organism, and resembling some kind of round,
hard Ulvacea?, like those which are seen in great quantity attached to the muddy shores
in shallow water.

Descending further down in the Lower Devonian and Upper Silurian, we see there also
the rocks saturated with petroleum, and generally marked by an abundance of Fucoidal
remains. It is probably from the rocks of the Upper Silurian that Prof. Brogniart ob-
tained his Fucoides from Canada. In Ohio and other Western States, where the Upper
Silurian limestone is barren of remains, it does not show any deposits of petroleum. In
Canada the same rocks have both Fucoides and fluid bitumen. Prof. Lesley, after an ex-
amination of the east end of Canada, Gaspe, wrote me (5th January, 1866) : " All sorts
of marine vegetation of Upper Silurian and Devonian ages seem there in great abundance,
and petroleum everywhere in the Devonian, and oozing from the lower Helderberg lime-
stone formation."

Still deeper the Lower Silurian has small deposits of bitumen in cavities of limestone,
even when every trace of organism has disappeared. This fact again is, I think, another
indication of the relation of petroleum to a marine vegetation. For it is well understood
that vegetable life has ruled the seas in its minute representatives, Diatomaceae, Desmi-
diaceae, long before animal life could be supplied or sustained by it. These diminutive and
primitive oil reservoirs are attributable to the concentration and decomposition of a local
surplus of that primordial vegetation.

The geographical distribution of petroleum and that of the remains of marine Algae
present the same remarkable coincidence. At Oil Creek, Slippery Bock Creek, in the
Chemung of Virginia, Ohio, Kentucky, everywhere indeed where oil has been seen, either
in cavities or saturating the rocks, and where the strata were open to view, a remarkable
amount of Fucoidal remains has been observed. This cannot be a mere casual coincidence.

The discussion presented in the last part of this paper may then be closed by this as-
sertion: That though the theory of the origin of petroleum from marine vegetables is not
yet supported by direct experiments and conclusive proofs, the reasons in favor of it are
weighty enough to merit due consideration. The more so, that if recognized true, the
theory presents an important chapter of the history of petroleum, and may prove of great
value in its application.

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