clay," which is a fossil soil on which a forest of Sigillariæ has grown, and the remains of these trees are very abundant in the coal and the accompanying beds. Hence the Sigillariæ of the coal-period are regarded as the plants most important in the accumulation of coal. In the Devonian, as far as we yet know, they did not attain to this utility, and in the lower part of the system at least, the rhizomata of Psilophyton seem to have occupied the place afterwards held by the Stigmariæ. In connection with this it is to be remarked that the Sigillariæ of the Erian period seem to have been few, and of small dimensions in comparison with those of the coal.

Rising still higher in the vegetable kingdom, and arriving at unquestionable Gymnosperms, we find in the Devonian of Eastern America, and also, I believe, in that of Scotland and Germany, trunks which may be referred to Coniferæ. In the Middle and Upper Devonian these present the structure of modern Araucarian pines, or that modification of it belonging to the Carboniferous trees of the genus Dadoxylon. In the Lower Devonian we have what seems to be a simplification of the Coniferous structure, in the cylindrical wood cells, marked only with spiral threads, found in the genus Prototaxites. These trees are very abundant as drift trunks in the Lower Devonian, down almost to its bottom beds, and sometimes attain to a diameter of three feet. Though of a structure so lax that it is comparable only with the youngest stems of ordinary Coniferæ, these trees must have been durable, and they are furnished both with medullary rays and rings of annual growth. Unfortunately we know nothing of their foliage or fruit.

But for one little fragment of wood we should have had no indication of the existence in the Erian of any trees of higher organization than the Conifers. This fragment, found by Professor Hall at Eighteen-mile Creek, Lake Erie, has the dotted vessels characteristic of ordinary Exogens, and unquestionably indicates a plant of the highest kind of

ferous; others are peculiar to the Devonian; and among these forms aliied to the modern Hymenophyllum and Trichomanes appear to prevail. One remarkable type, Cyclop teris (Archæopteris) Hibernicus, with its American allies, C. Jacksoni, etc., extends in the Upper Devonian over both continents, yet is wanting in the Carboniferous. Tree ferns also existed in the Devonian. Two species have been found by Dr. Newberry in Ohio, and remarkable erect trunks have been obtained by Professor Hall from Gilboa, in the State of New York. The latter are surrounded by aerial roots, and thus belong to the genus Psaronius; a genus which, however, must be artificial, since in modern tree ferns aerial roots often clothe the lower part of the stems while absent from the upper part. The only indication as yet of a tree. fern in the Old World is the Caulopteris Peachii, of Salter, from the Old Red of Scotland. It is further remarkable that the ferns of the genus Archæopteris are much more large and luxuriant in Ireland than in America, and that in both regions they characterize the upper member of the system.

Of the plants of the Paleozoic world, none are more mysterious than those known to us by the name Sigillaria, and distinguished by the arrangement of their leaves in vertical series, on stems and branches often ribbed longitudinally, and by the possession of those remarkable roots furnished with rootlets regularly articulated and spirally arranged, the Stigmariæ. It seems evident that this group of plants included numerous species, differing from each other both in form and structure. Still, as a whole, they present very characteristic forms dissimilar from those of their contemporaries, and still more unlike anything now living. I believe that many of them were Gymnosperms, or at the least, Acrogens with stems as complicated as those of Gymnosperms. In the Carboniferous period these plants have a close connection with the occurrence of coal. Nearly every bed of this mineral has under it a "Stigmaria under

clay," which is a fossil soil on which a forest of Sigillaria has grown, and the remains of these trees are very abundant in the coal and the accompanying beds. Hence the Sigillariæ of the coal-period are regarded as the plants most important in the accumulation of coal. In the Devonian, as far as we yet know, they did not attain to this utility, and in the lower part of the system at least, the rhizomata of Psilophyton seem to have occupied the place afterwards held by the Stigmariæ. In connection with this it is to be remarked that the Sigillaria of the Erian period seem to have been few, and of small dimensions in comparison with those of the coal.

Rising still higher in the vegetable kingdom, and arriving at unquestionable Gymnosperms, we find in the Devonian of Eastern America, and also, I believe, in that of Scotland and Germany, trunks which may be referred to Coniferæ. In the Middle and Upper Devonian these present the structure of modern Araucarian pines, or that modification of it belonging to the Carboniferous trees of the genus Dadorylon. In the Lower Devonian we have what seems to be a simplification of the Coniferous structure, in the cylindrical wood-cells, marked only with spiral threads, found in the genus Prototarites. These trees are very abundant as drift trunks in the Lower Devonian, down almost to its bottom beds, and sometimes attain to a diameter of three feet. Though of a structure so lax that it is comparable only with the youngest stems of ordinary Coniferæ, these trees must have been durable, and they are furnished both with medullary rays and rings of annual growth. Unfortunately we know nothing of their foliage or fruit.

But for one little fragment of wood we should have had no indication of the existence in the Erian of any trees of higher organization than the Conifers. This fragment, found by Professor Hall at Eighteen-mile Creek, Lake Erie, has the dotted vessels characteristic of ordinary Exogens, and unquestionably indicates a plant of the highest kind of

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v land plants, as yet altogether unknown to us. zoic was the age of Acrogens, the Eozoic may at of Anophytes and Thallophytes. Its plants nsisted of gigantic mosses and lichens, presenta phase of vegetable existence bearing the same. that of the Paleozoic which the latter bears to Le modern periods. But there is another and a ing possibility, that the Laurentian may have been I when vegetable life culminated on our planet, and in its highest and grandest forms, before it was into subordination to the higher life of the animal. tion of these questions belongs to the future of .. and opens up avenues not merely for speculation, for practical work.

above must be regarded as merely a sketch of the aspect of the subject to which it relates. Details sought elsewhere.-Nature.

INDIAN STONE IMPLEMENTS.*

BY J. J. H. GREGORY.

E stone selected for arrowheads and tomahawk points, as a rule, very hard in its nature, compact in structure, tine grained, presenting a conchoidal fracture when bro

In the valley of the Connecticut these conditions were -fied by a variety of hornstone, along the sea coast in porphyry. In each of these localities I have found some rowheads made of jasper, some of white granular quartz, nd occasionally one from slate, but the greater proportion of these are collectively small, though it is evident

*Observations on the Stone used by the Indians within the limits of Massachusetts, manufacture of their implements, with some remarks on the process of manuread at the Troy meeting of the American Association for the Advancement

ce.