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tinct evidence of the organic character of the wedgeshaped fronds. It is from the Utica shale, and elsewhere in the Siluro-Cambrian. It is just possible, as suggested by Hall, that this plant may be of higher rank than the Algæ.

The genus Palæophycus of Hall includes a great variety of uncertain objects, of which only a few are probably true Algæ. I have specimens of fragments similar to his P. virgatus, which show distinct carbonaceous films, and others from the Quebec group, which seem to be cylindrical tubes now flattened, and which have contained spindle-shaped sporangia of large size. Tortuous and curved flattened stems, or fronds, from the Upper Silurian limestone of Gaspé, also show organic matter.

Respecting the forms referred to Licrophycus by Billings, containing stems or semi-cylindrical markings springing from a common base, I have been in great doubt. I have not seen any specimens containing unequivocal organic matter, and am inclined to think that most of them, if not the whole, are casts of worm-burrows, with trails radiating from them.

Though I have confined myself in this notice to plants, or supposed plants, of the Lower Palæozoic, it may be well to mention the remarkable Cauda-Galli fucoids, referred by Hall to the genus Spirophyton, and which are characteristic of the oldest Erian beds. The specimens which I have seen from New York, from Gaspé, and from Brazil, leave no doubt in my mind that these were really marine plants, and that the form of a spiral frond, assigned to them by Hall, is perfectly correct. They must have been very abundant and very graceful plants of the early Erian, immediately after the close of the Silurian period.

We come now to notice certain organisms referred to Algæ, and which are either of animal origin, or are of higher grade than the sea-weeds. We have already discussed the questions relating to Prototaxites. Drepanophycus, of Goeppert, * I suspect, is only a badly preserved branch or stem of the Erian land-plant known as Arthrostigma. In like manner, Haliserites Dechenianus, of Goeppert, is evidently the land-plant known as Psilophyton. Sphærococcites dentatus and S. serra-the Fucoides dentatus and serra of Brongniart, from Quebec-are graptolites of two species quite common there. Dictyophyton and Uphantenia, as described by Hall and the author, are now known to be sponges. They have become Dictyospongiæ. The curious and very ancient fossils referred by Forbes to the genus Oldhamia are perhaps still subject to doubt, but are usually regarded as Zoophytes, though it is quite possible they may be plants. Though I have not seen the specimens, I have no doubt whatever that the plants, or the greater part of them, from the Silurian of Bohemia, described by Stur as Algæ and Characeæ,# are really land-plants, some of them of the genus Psilophyton. I may say in this connection that specimens of flattened Psilophyton and Arthrostigma, in the Upper Silurian and Erian of Gaspé, would probably have been referred to Algæ, but for the fact that in some of them the axis of barred vessels is preserved.

It is not surprising that great difficulties have occurred in the determination of fossil Algæ. Enough, however, remains certain to prove that the old Cambrian and Silurian seas were tenanted with sea-weeds not very dissimilar from those of the present time. It is further probable that some of the graphitic, carbonaceous, and bituminous

* "Fossile Flora," 1852, p. 92, Table xli.

+ Ibid., p. 88, Table ii.

† Brongniart, "Vegeteaux Fossiles," Plate vi., Figs. 7 to 12.

# "Proceedings of the Vienna Academy," 1881. Hostinella, of this author, is almost certainly Psilophyton, and his Barrandiana seems to include Arthrostigma, and perhaps leafy branches of Berwynia. These curious plants should be re-examined.

shales and limestones of the Silurian owe their carbonaceous matters to the decomposition of Algæ, though possibly some of it may have been derived from Graptolites and other corneous Zoöphytes. In any case, such micro

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FIG. 14. Silurian vegetation restored. Protannularia, Berwynia, Nematophyton, Sphenophyllum, Arthrostigma, Psilophyton.

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scopic examinations of these shales as I have made, have not produced any evidence of the existence of plants of higher grade, while those of the Erian and Carboniferous periods, similar to the naked eye, abound in such evidence. It is also to be observed that, on the surfaces of beds of sandstone in the Upper Cambrian, carbonaceous débris, which seems to be the remains of either aquatic or land plants, is locally not infrequent.

Referring to the land vegetation of the older rocks, it is difficult to picture its nature and appearance. We may imagine the shallow waters filled with aquatic or amphibious Rhizocarpean plants, vast meadows or brakes of the delicate Psilophyton and the starry Protannularia and some tall trees, perhaps looking like gigantic clubmosses, or possibly with broad, flabby leaves, mostly cellular in texture, and resembling Algæ transferred to the air. Imagination can, however, scarcely realise this strange and grotesque vegetation, which, though possibly copious and luxuriant, must have been simple and monotonous in aspect, and, though it must have produced spores and seeds and even fruits, these were probably all of the types seen in the modern acrogens and gymnosperms.

"In garments green, indistinct in the twilight,

They stand like Druids of old, with voices sad and prophetic."

Prophetic they truly were, as we shall find, of the more varied forests of succeeding times, and they may also help us to realise the aspect of that still older vegetation, which is fossilised in the Laurentian graphite; though it is not impossible that this last may have been of higher and more varied types, and that the Cambrian and Silurian may have been times of depression in the vegetable world, as they certainly were in the submergence of much of the land.

These primeval woods served at least to clothe the nakedness of the new-born land, and they may have sheltered and nourished forms of land-life still unknown to us, as we find as yet only a few insects and scorpions in the Silurian. They possibly also served to abstract from the atmosphere some portion of its superabundant carbonic acid harmful to animal life, and they stored up supplies of graphite, of petroleum, an gas, useful to man at the present day of them and draw their forms with t they themselves supplied.

NOTE TO CHAPTER II.

EXAMINATION OF PROTOTAXITES (Nematophyto HALLOW, OF MCGILL UNIVERSI

Prof. Penhallow, having kindly consented specimens, has furnished me with elaborate no conclusions, of which the following is a summ hoped will be published in full:

"1. Concentric Layers. The inner face of ea posed of relatively large tubes, having diameter micro-millimetres. The outer face has tubes rar 27.6 mm. The average diameter in the lower surfa that in the outer to 13.8. There is, however, no to the surface of the layers, though in some speci easily, with shining surfaces.

“2. Minute Structure. In longitudinal sect part of the structure consists of longitudinal tube length, and round in cross-section. They are appr but in some cases may be seen to bend sinuous direct contact. Finer myceloid tubes, 5.33 mm. erse the structure in all directions, and are belie from the larger tubes. In a small specimen suppo or small stem, and in which the vertical tubes are from one another, this horizontal system is very L but is less manifest in the older stems. The tubes no structure. The ray-like openings in the substa are evidently original parts of the structure, but no medullary rays. They are radiating spaces runni interrupted manner or so tortuously that they a rupted in their course from the centre towards th show tubes turning into them, branching into the mately horizontal, but tortuous. On the external specimens these radial spaces are represented by m

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