ART. XXXVII.-On Spore-cases in Coals; by J. W. DAWSON, LL.D., F.R.S.

WHEN in London, last spring, Prof. Huxley was kind enough. to show me some remarkably beautiful slices of coal mounted by his assistant, Mr. Newton, and showing with great distinctness multitudes of spore-cases and spores, some of them very well preserved. He farther stated to me his belief that such material had been largely or mainly instrumental in the production of Coal. At the time I declined to accept this conclusion, on the ground that the specimens probably represented layers of coal exceptionally rich in spore-cases; and that even in these specimens a large quantity of matter was present which long experience in the examination of coals enabled me to recog nize as cortical or epidermal matter, which I had previously shown by my examination of the coals of Nova Scotia to be the principal ingredient in ordinary coal. I promised, however, on my return to Canada, to look over my series of preparations of coal, with a view to the occurrence of spore-cases, and also to make trial of the somewhat improved method of preparation employed by Mr. Newton. On my return I gave the results of my examination to Prof. Huxley, in a letter which he has quoted in the brilliant exposition of his observations and conclusions in the Contemporary review for November,* and which will probably give a tone to the representations of popular writers on this subject for some time. While, however, admitting the great interest and importance of Prof. Huxley's observations, and prepared to contribute some additional illustrations of the occurrence of spore-cases in coal, I think it well to direct attention anew to the actual composition of the substance, as proved by its mode of occurrence, and illustrated by my own extensive series of observations on the coals of Nova Scotia and Cape Breton, including the series of eighty-one seams exposed at the South Joggins, the whole of which I have examined in situ and under the microscope.

The occurrence of bodies supposed to be spore-cases in coal, is, as Prof. Huxley states, no new discovery; but in reality these may be said to be the first organisms recognized by any microscopic observer of coal-that is, if all the clear spots and annular bodies seen in slices of coal are really spore-cases. They were noticed by Morris as early as 1836, and they had been observed and described long before by Fleming in Scotland. Goeppert mentioned and figured them in his "Treatise on Coal" in 1848. Balfour described them in 1859 as occurring in Scottish coals, and Quekett figured them in his account of the

* In the quotation the word "cubical" has been substituted for "cortical."

Torbane Hill mineral in the same year. In 1855 the latter microscopist showed me in London slices exhibiting round bodies of this kind, very similar to those now described by Huxley; but at that time I regarded them as concretionary, though Prof Quekett was disposed to consider them organic. Mr. Carruthers has summed up most of these facts in his account of his genus Flemingites in the Geological Magazine for October, 1865. The subject has also attracted the attention of microscopists in connection with the Tasmanite, or "white coal" of Tasmania, which is composed in great part of the spore cases of ferns.

I suppose that the oldest spore-cases known are those described by Hooker from the Ludlow formation of the Upper Silurian; but these, if really spore-cases, are different in structure from those ordinarily found in the coal-formation, more especially in the great thickness of their walls, and I am not aware that they have anywhere been found in considerable quantities. The oldest bed of spore-cases known to me, is that at Kettle Point, Lake Huron. It is a bed of brown bituminous shale, burning with much flame, and under a lens is seen to be studded with flattened disc-like bodies scarcely more than a hundredth of an inch in diameter, which under the microscope are found to

2.

3.

Fig. 1, Part of a slice of shale from Kettle Point, 70 diameters. Figs. 2 and 3, Spore-cases from the

showing two spore-cases and remains of spores. same, as opaque objects. 70 diameters.

be spore-cases, slightly papillate externally, and with a point of attachment on one side and a slit more or less elongated and gaping on the other, figs. 1, 2, 3. I have proposed for these bodies the name Sporangites Huronensis. When slices of the rock are made, its substance is seen to be filled with these bodies, which, viewed as transparent objects, appear yellow like amber, and show little structure, except that the walls can, in some cases, be distinguished from the internal cavity, and

the latter may be seen to inclose patches of flocculent or granular matter. In the shale containing them there are also vast num bers of rounded translucent granules which may be the escaped spores.

The bed at Kettle Point is stated in the report of the Geological Survey to be 12 to 14 feet in thickness; but to what degree either in its thickness or horizontal extent it retains the characters above described, I do not know. It belongs to the Upper Devonian, being supposed to be a representative of the Genesee

slates of New York. It contains stems of Calamites inornatus and of a Lepidodendron, obscurely preserved, but apparently of the type of L. Veltheimianum, and possibly the same with L. primavum of Rogers. The spore-cases are not improbably those of this plant, or of the species L. Gaspianum, which belongs to the same horizon, though not found at this locality. The occurrence of this bed is a remarkable evidence of the abundance of Lycopodiaceous trees, whose spores must have drifted in immense quantities in the winds, to form such a bed. It is to be observed, however, that this is not a bed of coal, but a bituminous shale of brown color, and with pale streak, no doubt accumulated in water, and even marine, since it contains Spirophyton and shells of Lingula. In this it agrees with the Australian Tasmanite, which, though composed in great part of spore-cases of Ferns, is, as I am informed by Mr. Selwyn, an aqueous deposit, containing marine shells.

There is, however, one bed of true coal known in the Devonian of Eastern America, that of Tar Point, Gaspé, and it is curious to observe that this is not composed of spore-cases, but of successive thin layers of rhizomata and stems of Psilophyton, with occasional fragments of Lepidodendron and Cyclostigma. Rounded disks, which may be spore-cases, occur in it, but very rarely. In the bituminous shales associated with this coal, the microscope shows amber-colored flakes of irregular form, but these are easily ascertained to be portions of the epidermis of Psilophyton, or of the chitinous crusts of crustaceans which abound in these beds.

Ascending to the Lower Carboniferous (sub-carboniferous). there are great quantities of rounded spore-cases of the size of mustard seeds (Sporangites glabra of my papers) in the rocks of Horton Bluff and Lower Horton, Nova Scotia. They are sometimes globular, and filled with pyrite of a granular texture which perhaps represents the original cellular structure or the microspores. In other cases they are flattened and constitute thin carbonaceous layers. They are almost without doubt the spore-cases of Lepidodendron corrugatum, which abounds in the same beds, and constitutes in one place a forest of erect stumps. I described them in a paper on the Lower Carboniferous of Nova Scotia in the Proceedings of the Geological Society of London for 1858, though not then aware of their true nature, which was, however, recognized by Dr. Hooker in some specimens which I had sent to London.

In my paper on the conditions of accumulation of Coal, (Proceedings of Geological Society of London, May, 1866), Í proposed the name Sporangites for these bodies, in consequence of the difficulty of referring them certainly to any generic

The well known Cauda-galli fucoid.

forms. Carruthers had in Oct. 1865, described a cone containing rounded spore-cases of not dissimilar type, under the name Flemingites. In the paper above referred to, I stated that out of eighty-one coals of the South Joggins Section examined by me, I recognized these bodies and other fruits or Sporangia, in only sixteen; and of these only four had the rounded Lycopodiaceous spore-cases similar to those of Flemingites. These are the following:

(1.) Coal group 12, of Division IV, has a bed of coal one foot thick, of which some layers are almost wholly composed of Sporangites papillata.

(2.) Coal group 13, Div. IV, has in some layers great quantities of Sporangites glabra, especially in the shaly part of the coal. (3.) In Coal group 14, Div. IV, a shaly parting contains great numbers of similar Sporangites.

(4.) In Coal group 15a, Div. IV, the shaly roof abounds in sporangites, but I did not observe them in the coal itself.

In addition to these cases, all of which curiously enough occur in one part of the section, and among the smaller coals, I have noted the occurrence of clear amber spots in several of the compact coals, but I did not regard these as certainly organic, suspecting them to be rather concretionary or segregative structures.

4.

The great coal beds of Pictou are, in so far as my observation has extended, remarkably free from indications of spore-cases, and consist principally of cortical and ligneous tissues with layers of finely comminuted vegetable matter. A layer of cannel, however, from a bed near New Glasgow has numerous flattened amber-colored discs, which may be of this character. In those of Cape Breton, the yellow sporecase-like spots are much more abundant; but these coals I have less extensively examined than those of the mainland of Nova Scotia. Of American coals, the richest in spore-cases, that I have seen, is a specimen from Ohio, which contains many large spore

cases, and vast numbers of more ing at one side a part of a large spore-case, minute globular bodies apparently

macrospores. It quite equals in this respect some of the English coals referred to by Huxley, (fig. 4). I have also a specimen of anthracite from Pennsylvania, full of spore-cases, some of them retaining their round form and filled with granular matter which may represent the spores.

It is not improbable that sporangites or bodies resembling them, may be found in most coals; but the facts above stated

indicate that their occurrence is accidental rather than essential to coal accumulation, and that they are more likely to have been abundant in shales and cannel coals, deposited in ponds or in shallow waters in the vicinity of Lycopodiaceous forests, than in the swampy or peaty deposits which constitute the ordinary coals. It is to be observed, however, that the conspicuous appearance which these bodies and also the strips and fragments of epidermal tissue, which resemble them in texture, present in slices of coal, may incline an observer, not having large experience in the examination of coals, to overrate their importance, and this I think has been done by most microscop ists, especially those who have confined their attention to slices prepared by the lapidary. One must also bear in mind the danger arising from mistaking concretionary accumulations of bituminous matter for sporangia. In sections of the bituminous shales accompanying the Devonian coal above mentioned, there are many rounded yellow spots, which on examination prove to be the spaces in the epidermis of Psilophyton through which the vessels passing to the leaves were emitted. To these considerations I would add the following, condensed from my paper above referred to, in which the whole question of the origin of coal is fully discussed.*

(1.) The mineral charcoal or "mother coal" is obviously woody tissue and fibers of bark; the structure of the varieties of which and the plants to which it probably belongs, I have discussed in the paper above mentioned.

(2.) The coarser layers of coal show under the microscope a confused mass of fragments of vegetable matter belonging to various descriptions of plants, and including, but not usually largely, sporangites.

(3.) The more brilliant layers of the coal are seen, when separated by thin laminae of clay, to have on their surfaces the markings of Sigillaria and other trees, of which they evidently represent flattened specimens, or rather the bark of such specimens. Under the microscope, when their structures are preserved, these layers show cortical tissues more abundantly than any others.

(4.) Some thin layers of coal consist mainly of flattened layers of leaves of Cordaites or Pychnophyllum.

(5.) The Stigmaria underclays and the stumps of Sigillaria in the coal roofs equally testify to the accumulation of coal by the growth of successive forests, more especially of Sigillariæ. There is on the other hand no necessary connection of sporangite beds with Stigmarian soils. Such beds are more likely to be accumulated in water, and consequently to constitute bituminous shales and cannels.

* See also Acadian Geology, 2d edit., pp. 138, 461, 493.