that they are due to the arrangement in linear series of the elongated cells composing the prosenchymatous tissue of this layer, and as such are to be distinguished from the lines which are occasionally seen running up the lateral parts of the ribs of some corticated specimens, which shew the outer surface of the cuticle,* and which lines I look upon as having a totally distinct origin, as resulting in fact from the horizontal extension of the stem. It is by means of these longitudinal striæ that I have arrived at the conclusion, that Lindley and Hutton's figure of Sigillaria flexuosa does not exhibit the original or external surface of the cuticle of this so-called species.

It has been previously remarked, that I have not met with any single specimens of this fossil shewing different surfaces of the cuticle: it is probable, however, that Sigillaria hexagona (Brong. Pl. 155) is in this state; the part shewing the leaf-scars with a well-defined border is obviously the external surface of the plant,-that which shews these scars with a less defined border, appears to be the external surface of the inner layer of the cuticle,—and the one which exhibits this character of the scars very obscurely, is probably the impression of the inner surface of the same layer. That the last part alluded to does not exhibit the matrix on which the specimen is preserved, worn down below the impression which ought to result from the inner surface of the inner layer of the cuticle, is, I think, fully proved by the longitudinal striæ thereon exposed being so strongly marked. I would also suggest that the various appearances exhibited by the figures of Sigillaria Knorri (Brong. Pl. 156, fig. 3) may be similarly produced.

In none of the descriptions of Sigillaria that have come under my notice, is there any mention made of this plant possessing axillary buds. That such constituted one of its characters can admit of little if any doubt, after an examination of the outline † which is given in our plate of illustrations, and which is a facsimile of one of the leaf-scars of a specimen in the Newcastle Museum, resembling Brongniart's Sigillaria scutellata, in the width of its ribs and the distance of the scars from each other What I wish to call attention to in this outline is the prominence c above the margin of the leaf scar a, a character which is seen above the whole of the scars exhibited in the specimen. Now, their situation relatively to the leaf-scars being the same as that of the axillary buds of Dicotyledons, and their occurrence above all the scars of the specimen, is, I think, equivalent to a demonstration that these prominences are the remains of the axillary buds of the plant on which they are preserved. This character, taken in connexion with what has been stated of the branching

* Vide Brongniart's figure of Sigillaria reniformis.

↑ Vide Plate I, figure 6-a the vascular scar--b the triple series of vascular scars-c the axillary bud.

I have observed similar prominences, though they are not so obvious, on some other specimens of Sigillaria; but instead of being a little above the leaf scar, they are in close contact with its superior margin,-a position which, it is evident, must render it difficult to see them.

of the North Biddick and other specimens, is, in my estimation, quite conclusive in proving that the branches of Sigillaria originated, as in the higher vegetable forms, from the axils of the primary leaves.*

In accordance with the preceding remarks respecting the bipartition of the cuticle of Sigillaria, we are naturally led to arrange a number of specimens, in the states represented by the diagrams, under three separate divisions. These divisions may be severally termed corticated, demicorticated, and decorticated.

The corticated division will embrace those specimens having the entire cuticle preserved; the demicorticated such as have only one of the layers of this part remaining, and the decorticated those which are divested of both layers.

Corticated specimens will exhibit two different appearances accordingly, as the inner or outer surface of the entire cuticle may be exposed; for instance, in the latter case we shall have leaf-scars on the ribs, but in the former there will be vascular scars on broad furrows. Examples of the first kind are of exceedingly rare occurrence in the North of England coal-field; nearly all that are published in the "Fossil Flora" from this district are either decorticated or exhibit only the inner surface of one or other of the two layers composing the cuticle: the figures representing Sigillaria alternans, Sig. catenulata, Sig. reniformis (Tab. 71), and some others, may be taken as examples of the last kind.

Demicorticated specimens are extremely difficult to recognise, on account of the appearance which they present being somewhat similar to that displayed on the inner surface of the inner layer of the cuticle, and consequently they may resemble the kinds last mentioned. Demicorticated specimens are also divisible into two kinds, the one having the vascular scars on ribs, and the other on broad furrows. As already suggested, Brongniart's figures of the genus Syringodendron, and I may also add some of those given by Sternberg‡ and Lindley and Hutton as ex

I have also observed axillary buds on several specimens of Lepidodendron, -a character which completely proves that the branches of this plant have had an origin similar to those of Sigillaria, and not from a division of the point of the main stem at certain stages of its developement, as is generally considered. Sternberg's figures of Lepidodendron aculeatum (Tab. vi. fig. 2; Tab. viii. fig. 1. B. a. b.), are the only published ones known to me that exhibit these axillary buds; the fossil is merely an impression, consequently, the figures shew them in the state of impressions.

+ The fact already stated respecting the occasional flexuous appearance of the longitudinal strice, on the ribs of the North Biddick specimens, will in a great measure shew that this character is not sufficient to constitute a specific difference.

The specimen on which Sternberg founded his genus Syringodendron (Tab. xiii. fig. 1), appears to be nothing more than a decorticated portion of Stigmaria (root of Sigillaria) belonging to a part adjacent to the stock. The irregularities of the furrows, and the irregular arrangement of the vascular scars of this specimen

amples of this genus, may represent different species of Sigillaria in a demicorticated state.

Decorticated specimens are by far the most abundant. Lindley and Hutton's figure of Sigillaria reniformis (Pl. 57), affords a good illustration of the kind displayed on that division of the diagram 4, marked B ; while Brongniart's representation of Sig. pyriformis (Pl. 153, fig. 3), shews the appearance on the division marked A of diagram 3; the former exhibits an impression of the inner surface of the cuticle, and the latter shews an impression of the outer or original surface of this part.* I have a single observation to make respecting specimens of the first division, which is, that they expose the vascular scars situated on convex ribs, with the exception of the previously noticed specimen from North Biddick. It is necessary to bear this in mind, as it is highly probable that hand specimens may be found displaying the same character, and as such will be otherwise inexplicable.

What has now been stated will, I think, make clear the mode in which one specimen of Sigillaria may afford six different appearances; should this be admitted, it necessarily follows, that, of the sixty or more species which have been described of this genus, a great many are purely factitious: other considerations to be adduced hereafter will tend still further to reduce this number.

(To be continued.)

United States Exploring Expedition.

ENGLAND and France have long been honourable rivals on the ocean, as well in exploring as in warlike expeditions. The voyages of Cook, Vancouver, Flinders, Parry, Beechey, King, Fitzroy, and Ross, are conspicuous in the annals of English navigation; while France is no less honoured by her explorations under Bougainville, La Perouse, Labillardière, Duperrey, Freycinet, and D'Urville. Both countries have looked beyond the mere discovery of new lands, new commercial resources, and territorial aggrandizement. Their efforts have been directed towards an increase of knowledge in every branch of science; and there are few regions, from the equator to the poles, which have not been tracked by their vessels. What

are precisely the same as is seen on the origins of the branches of this fossil; that is, when the characters of the stem become blended with those of the root. * The so-called Sigillaria monastachya (Pl. 72) of Lindley and Hutton, which I perceive is erroneously considered by Presl a species of Ulodendron (Sternberg, parts 7 and 8, p. 186) is, I am convinced, a decorticated isolated rib of Sig. reniformis. The specimen figured in the Fossil Flora is in the Newcastle Museum.

ever could illustrate the condition or resources of the regions visited; the customs, languages, or history of their unknown tribes; or the motion of the winds, the waters, the world, or the stars, has been thought worthy of observation. Cook was dispatched to the Pacific Ocean expressly to observe the transit of Venus, and Sir Joseph Banks and Forster accompanied him at different times in his voyages around the world. In the late voyage of Fitzroy, Mr Darwin was associated with the expedition, and made large contributions to science. France has outstripped England in the liberality with which her expeditions have been fitted out, and in the magnificence of her publications. The many folio volumes of plates, published as the result of the voyages of Freycinet, Duperrey, and D'Urville, and those of Napoleon's expedition into Egypt, are among the most splendid productions of the age. They are a noble gift from France to the world.

America has at last taken her part in the labours of exploration. An Exploring Expedition has been sent out, and has returned. It was organized on a plan honourable to a nation that is second to none in enterprise and general education; and its results, when published, will, it is believed, equal in amount and interest those of any expedition that has preceded it. The expedition sailed under the command of Lieutenant Charles Wilkes, who was aided by intelligent officers, wellfitted for the duties to which they were called; and the large number of charts that have been made in the course of the cruise, evince alike the energy of the commander, and the industry and skill of all engaged in the surveys. The duties have been extremely laborious, beyond the conception of the comfortable house-dweller at home. The loss of one schooner with all hands, including two officers; the total wreck of another vessel-the sloop of war Peacock-stripping the crew of everything but their lives; the massacre of two officers by the savages of the Feejee islands, and of a sailor by the treacherous Kingsmill Islanders, are the only fatal disasters; but they are a few only of its perils. Indeed, there were dangers everywhere, by land as well as by sea. The personal adventures in the course of the cruise, told as simple tales, without exaggeration, would make a volume full of startling incidents, and replete with interest.

It is gratifying to learn that the country will soon be put in possession of the facts collected. Thus far those engaged in it have alone been benefited. They have collected information that will be invaluable to them as men of intelligence and members of society. It remains for them to give this information to the country, that the people who have borne the expense may also partake of the profits. The affairs of the expedition are in the hands of the Library Committee of Congress, and, under their direction, Captain Wilkes has been put in charge of the history of the voyage, the charts, and philosophical observations, and the other departments of science are placed in the hands of those that had charge of them during the voyage. Each will prepare his own reports, reap his own honours, and be held responsible for his own facts. The extent of the work cannot be definitely stated: the plates will form several folio volumes in the style of the voyage of the Astrolabe.

As the country is much interested to know what has been done by the expedition, it is proposed to give, in as brief a manner as possible, some idea of the material on hand for publication, and the general character and extent of the collections. Our acquaintance with the gentlemen of the expedition enables us to state many particulars which have not yet appeared in print, the accuracy of which may be relied on. We prelude our remarks, by giving the track of the vessels as laid down in Captain Wilkes's synopsis of the cruise.

On August 19, 1838, the vessels left the Capes of the Chesapeake, and sailed for Rio Janeiro, making short calls at Madeira and the Cape Verds. From Rio, on the 6th January following they proceeded to Rio Negro, on the northern confines of Patagonia, and thence to Nassau Bay, in Terra del Fuego, just west of Cape Horn. From this place, the Peacock, Porpoise, and the two schooners, made cruizes in different directions towards the pole; but the season was too far advanced for much success, as it was already February 24th before they sailed. The schooner Flying Fish, notwithstanding, reached latitude 70° 14' S., nearly the highest attained by Cook, and not far from the same longitude. The ship Relief was ordered to enter a southern channel opening into the Straits of Magellan, but met with constant gales, and barely escaped being