eren in the same district of a country; but, in particular, that the same species sheds its leaves at very different periods, in different countries. In both instances, the difference of the time of defoliation seems to depend, principally, upon a difference of season, or of climate. Extreme heat and extreme cold are both observed to be favourable to the fall of the leaf. In the hot summers, the leaves of many plants lose their verdure, and fall a full month earlier than they do in milder reasons. 5. The fall of the leaf is almost always preceded by a very essential change in its cofour. Yellow, red, and brown, are the most common colours of the dying leaf, About the close of September (sooner or later according to the season), the forest trees in Pennsylvania, and other middle parts of the United States, begin to lose their verdure. The leaves assume new colours, particularly yellow and red, or crimson. Nothing can be more picturesque than an American forest at this season. The beauties of the scenery will be described by some future Thomson; or exhibited on canvas by the pencil of an American Salvator Rosa. It will be sufficient for me to observe, that the leaves of almost all the species of juglans (walnuts and hickery) and maple, assume different shades of yellow; whilst those of nyssa integrifolia, called gum, the laurus sassafras, the cornus florida, or dogwood, and others, are clothed in a livery of crimson or red." If the author had completed his original design, the second part would have been considerably extended: but having been drawn out, in the first and third parts, to discussions of greater length than he expected, he was obliged to restrain himself within narrower limits in the second, which, for reasons which do not appear, were sent last to the press. In consequence of this alteration of his plan, there were several references in the first part to future explanations and enquiries which are no where to be found. These the English editor has properly expunged; though one instance at least has escaped his notice. And as "probably, in the ardour of composition, Dr. Barton had sometimes anticipated himself, and introduced into the technical part of the work several things, which, as he himself at the time was not insensible, more properly belong to the physiology, they are removed in the English edition to this part of the work, and the whole placed in a connected series, from a persuasion, not only that they will be read with greater pleasure and advantage, but also that the elementary part will be consulted with greater readiness, when freed from this foreign matter." The anatomical structure of the trunk and leaves is explained at large, and the opinions of the best authors on the subject are distinctly detailed. But the sections that relate to the bractes, the calyx, the corolla, the nectary, the pollen, the pistillum, and the pericarp, consisting entirely of the observations which were incidentally introduced by the author into the first part, are much less full and comprehenwhich these organs are supposed to be sive, and are confined to the uses to subservient in the vegetable economy. The same imperfection, however, does not attach to the section on the anatomy of the seeds, which also stood originally in the first part. It is extended to a considerable length, and contains a well digested summary of Gartner's ideas on this essential and important part of a plant. In the explanation of the Linnæan system, which constitutes the third and concluding part of the work, the author gives not only the character of each class and order, but also their relation sometimes of Jussieu, with the medical to the natural orders of Linnæus, and and economical uses of such species as have been made conducive to the health, food, or convenience of mankind. That our readers may form a judgment of the information they may expect to receive on these heads, we shall select what is said of the class enneandria, chiefly because it lies within a small compass, "With respect to the genera which be long to the class enneandria, they constitute different assemblages of vegetables, more or less natural. Laurus, anacardium, rheum, together with callitriche, blitum, corispermum, rumex, polygonum, and several others, which have already been mentioned, as be longing to preceding classes; and also cerceeding classes, constitute Liunaus's twelfth tain genera which are arranged in the suc order, Ioloracee, which I do not think entitled to the name of a natural order. The genus laurus gives name to an order in the system of M. de Jussieu. It is the fourth order of his sixth class. In the system of the same learned naturalist, there is an order, entitled, polygoneæ, which embraces one of the genera of the class enneandria: the genus rheum, (rhubarb), butomus, together with calamus, juncus, triglochin, and some others, belong to Linnæus's fifth order, tripetaloi-, deu. The class enneandria, though a very small class, contains a number of important vegetables. Different species of laurus are highly important for medical or domestic purposes. Camphor is the produce of the laurus camphora, cinnamon of the laurus cinnamomum, and cassia of the laurus cassia. To the laurus benzoin, the people of the United States have ascribed useful medical powers. The laurus sassafras, or sassafras, is entitled to the attention of physicians. The leaves of the laurus borbonia are used as a spice in some parts of the United States. The laurus nobilis, which the Greeks called Aapn, is the species which was dedicated to Apollo, and employed as a crown or garland for the heads of the Roman emperors, pontiffs, and poets. "The different species of rhubarb are vaIable cathartics, particularly the rheum palmatum, or palmated rhubarb. I think it not improbable that North America possesses some native species of this genus. Be this as it may, the cultivation of rhubarb ought to be atiended to in the United States. The United States possess few plants of the class enneandria. It is true that several species of laurus are natives of this great tract of country; but our species are by no means constantly furnished with nine stamens: thus, laurus sassafras is sometimes found dioicons, and laurus borbonia belongs to decandria. Butomus (flowering rush) is the only British plant." Dr. Barton condemns, in pointed terms, Gmelin's junction of the classes icosandria and polyandria, and does not concur with Thunberg in abolishing gynandria, with monæcia, and diæcia ; but agrees Dr. Smith and others in referring the ge nera of syngenesia monogamia to pentandria; is of opinion that the class poly. gamia ought to be suppressed; and cannot help thinking that the sexual system would be improved, if the genera of dodecandria, which have more than ten stamens, were removed to polyandria, and the rest disposed of in different class es, according to the number, insertion, &c. of the stamen. The value of the work is considerably enhanced by the addition of thirty plates, most of them engraved from the original drawings of Mr. William Bartram, of Ringsessing, in the vicinity of Philadel phia, and chiefly representing Americas plants which have not before been i gured. ART. VI. Miscellania naturalia, sine Dissertationes varia ad Historiam naturalem ¿estantes. Autore A. H. HAWORTH, Linn. Soc. Londini socio. THESE dissertations are annexed to the Lepidoptera Britannica reviewed in a preceding article; but as the latter work, when completed, will be of size sufficient for a volume; and as the author intends to publish several other dissertations similar to the present, which, connected with them, will form another, we have been induced to consider them as distinct works, and on account of their subject, to place these dissertations in the botanical part of our present chapter. The first, and most considerable, is a new arrangement of the genus mesembryanthemum, and descriptions of such species as were not described before, with their places of growth, duration, and times of flowering. This genus has long been a favourite with the cultivators of exotic plants, on account of the singularity of some species, and the beauty of others: but unfortunately they make no figure in the herbaria of botanists, owing to the impossibility of preserving most of them in a dried state, with any tolerable resemblance to the general form of the growing plant, and, still less, so as to C discriminate their minuter, but often esential, characteristic parts. Only fortyfive were known to Linnæus; and addition was made to the list by Re chard: Willdenow enumerates 86: cr author has increased them to 211; moti than 160 of which he himself possesses a living state. Having long entertain:: a strong predilection for this curious ge nus, he published observations upon about ten years ago. Since that time be has greatly increased his collection, an has had the satisfaction to see varia species perfect their flowers, he believe for the first time in Europe. He ha now, therefore, published all the knew species, describing distinctly the parts t fructification of such as are new, w specific characters, often improved, those which he had before describe but referring his readers to his form work for particular details. We suppos that he was restrained by a delicate, ar in itself laudable, unwillingness to make the lovers of a favourite science purcha the same matter twice; but we shou have been better pleased if he had inc porated into this all that is essential in the former publication, and thus made one complete whole. In a course of study, every one must expect to be sometimes referred from one book to another for further information. But, even though the other book is at hand, which cannot always be the case, the trouble which it gives is so tedious and perplexing, and, with the utmost care, it is so often productive of mistakes, that we could wish to have it prevented as much as possible. As some of the sections in the former observations were not universally approved, Mr. Haworth has re-arranged and new modelled the genus, in a manner which he conceives will not admit of farther improvement or alteration. His present divisions are thirteen. 1. Minima. Acaulia, obconica, seu obcordata, vel rarius sphæroidea; foliis retusissimis & usque ad apices connatis; floribus sessilibus. 4. Subacaulia. Caulibus nullis vel brevissimis, radice perenni, Subdivided into moniliformis, integrifolia, denticulata & linguaformis; the last divided again into disticha, cruc ata, albreviata, & dolabriforme. 3. Prostrata. Caulibus prostratis, foliis confertis elongatis, petalis vel utrinque, vel intus luteis. 4. Capitata. Foliis densissime alternis capitatis longissimis ; caule senectute decumbente, petalis a basi ad medium ciliatis. 5. Planifolia. Foliis planis sæpe subcarinatis; caulibus sæpe decumbentibus prostratis effusis. Subdivided into annua, which are either undulata, with undulated or pinnatifid leaves, or integra with leaves entire and not undulated; biennia, perennia, & incognita, seu radice ignota. 6. Canali ulata. Foliis linearibus, juni. oribus canaliculatis subtus convexis, ramis sæpe suffrutescentibus, radice sæpe perenni, rarius annua. Subdivided into annua, spinulifera, & varia. 7. Vesperiflora. Caulibus suffrutescentibus gracilibus duris, & in hoc genere valde defoliatis, foliis teretiusculis impunctatis, calycibus quadrifidis, corollis odoratis intus albis, radicibus ætate car. noso-incrassatis, fibris perpaucis. 8. Rubicunda. Ramis suffrutescentibus glabris, foliis (divisione prima excepta) compresso-triquetris nudis, apicibus iec ANN. REV, VOL. III. tis: petalis (m. edule heterophyllo & dilatato exceptis) rubicundis. Subdivided into teretiuscula, compressa, falcata, scabrida, brevifola, & reptantia. 9. Flaviflora. Caulibus suffrutescentibus sæpe erectis, foliis triquetris sæpe brevissimis, petalis flavis, aurantiis vel coccineis. Subdivided into perfoliosa, tardiflora, & frequentiflora. 10. Adunca. Foliis distinctis (sine vaginis incrassatis) apicibus plus minusve aduncis, petalis rubicundis, caulibus suffrutescentibus, rarissime reptantibus. Subdivided into claudentia, with flowers closing at night, and inclaudentia, with flowers not closing. 11. Perfoliata. Caulibus duris lignosis, foliis valde connatis triquetris; vaginis carnosis, apicibus aduncis; floribus sæ pius albis, rarius rubicundis. Subdivided into axillaria, & panicu lata. 12. Aspericaulia. Caulibus suffrutescentibus, ramulis plus minusve scabris. 13. Hispida. Ramulis vel foliis vel apicibus foliorum plus minusve hispidis. Subdivided into hispicaulia, hispifulia, & barbifolia. We cannot refrain from entering a strenuous protest against the terms rubie cunda, & flaviflora, employed as names of divisions. They are manifestly improper; first, because both of them contain species with flowers of different colours from those indicated by their names; and secondly, because there are flowers of those colours in the other sections. A similar objection may be made to the term adunca. All classical, ordinal, generic, and sectional significant names, should be strictly exclusive, and completely comprehensive. The generic, essential, and natural characters, prefixed to the enumeration of the species, are entirely new, and are so drawn up as to include the whole; a work of no small labour, and at the same time of no less importance. It has been too much the practice, even of good botanists, to pay a superstitious regard to the generic characters of Linnæus, without attending to the alterations which are be come absolutely necessary by the dis. covery of new species, evidently belong. ing to the same genus, though they differ from the former species in some of the parts of fructification. A generic character, comprehending the calyx, corolla, stamen, pistil, germen, pericarp, and 3 C seed, must necessarily be lax in many particulars. The essential character, on the other hand, being formed from one or two, should not contain a single iota which does not exist in every species. A natural character, taking in all the parts of the plant, must, in every large genus, be unavoidably so prolix, and in many cases so perplexing, even when it is not in itself confused, that we have some doubt whether it be really worth the time and trouble required to draw it up. In all monographs, and local floras, it should, as far as practicable, be separately formed for each species. The specific characters, descriptions, &c. are in Latin; the occasional observations, as in the Lepidoptera Britannica, are in English. Those annexed to m. floribundum contain so much new and curious matter that, though longer than we wish, we cannot resist the temptation to lay them before our readers. "Obs. 1. The mature and exsiccated capsules of many, and probably of all mesembryanthema, but of this species in particular, possess, in a very lively manner, the proper ties of an hygrometer. In showery weather in autumn I have seen thein expand, and contract themselves again, several times in the course of a day. When expanded, they have a pretty, but very unusual appearance, and resemble considerably the flowers of a sta pelia; but their segments are more obtuse. If the dried capsules are well moistened with water, or any other fluid of equal tenuity, they will unfold themselves in the course of a few minutes; and, when dried again, they will spontaneously close up. The cause of this unusual sensibility, on the access of humidity or drought, is exceedingly interesting, and but little understood. In order to make it intelligible, I must first explain the interior structure of the valres of the capsule, and indeed of all its inner parts; for upon their conformation depend entirely the above mentioned motions. In the centre of the mature exsiccated capsules, when expanded, are seen five concave, obcordated, and some what trapeziform menzbranes, which are in close contact, and form the figure of a rose, that stretches horizontally, in the manner of an awning over (but not in contact with) the ripe seeds, which appear to lie beneath it in their proper cells; but are in this state easily dislodged by the smallest force. The five seg ments of the expanded capsules on their interior surfaces, are cach bisecurigenous; that is, each of the segments is furnished with two parallel (but at their points divaricating) hatchet-shaped callosities, or springs, which are attached longitudinally, but edgeways, to the capsular segments; their bases are insert ed into the obcordated bases of the abhre mentioned central membranes, and their apices are cach joined to another membrane, nearly of a semilunar shape, which, (standing up perpendicularly in the centre of the cap most erect part of their apices, and then sular segments) surrounds the exterior and unites them to the apices of the capsular seg ments. The semilunated membranes are themselves united at their tips; they stand up nearly erect, and form a pellucid connecting arch between the two hatchet-shaped springs, and enable them to dilate and contract in per fect unison. This membranous arch, from dicularly, and nearly central on the capsular spring to spring, stands up almost perpen segments, and forms a very interesting appear ance. Through the arch-way may be seen in profile (for it stretches over a perfect vacuity) the different parts above described. of m. "Now upon the dilatation and contraction of their hatchet-shaped springs, entirely de pend the opening and closing of the capsules fect and lively hygrometers are affected by the floribundum. The springs being per access of humidity or drought. In wet wea tended; in dry they are tightened and con ther their component parts are dilated and es tracted. When the springs are dilated, they forcibly push open the segments of the ear sule in an horizontal manner; but when they are contracted, they draw them up and clos with an equal force, and this often more than once (and that naturally) in the course of the same day. "Obs. 2. In every stage of these extraordinary occurrences, I behold and conten plate the wise contrivances of an omnipotent creator. These hamble vegetables are hereby enabled to sow their seeds, at that moment of time which is unquestionably the must proper for them; that is, when the sandy de sarts of their nativity are moistened with the seasonable blessings of rain, which not only assists in expelling the seeds from their ex panded lodgements, but absolutely imbes them in a soit prepared for their reception." The second dissertation relates to the genus tetragonia, nearly allied to me sembryanthemum. After a concise his tory of the genus, with the generic names by which some or other of its species have been distinguished in the works of different authors, nine species are enumerated, eight of which had been already admitted by Thunberg and Willdenow. Seven of these are technically described from living plants in the possession of the author: the hirsuta he has not seen either recent or dried, and the spicata only once in the royal garden at Kes, but without an opportunity of composing a description. The third dissertation has for its sub ject the genus portulaca, uniformly misspelt, in the present work, portulacca. This genus has been divided by Jussieu, Willdenow, and others, into two, but, as Mr. Haworth thinks, not with sufficiently constant and appropriate generic distinctions. Willdenow in particular has confined the generic name portulaca to those which have a capsula 1-locularis, circumscissa; and has placed under the new genus talinum those which he conceives have a capsula 3-valvi‹ & semina arillata. But that these are not real generic distinctions our author is convinced by four nondescript species, which induced him to study the genus, and occasioned the present dissertation, under the disadvantage of having had no opportunity of ex amining more than eight other species. These new species are so nearly allied to p. anacampseros, that they cannot with propriety be separated from it, and yet have not the 3-valved capsule attributed to talinum, under which it has been lately arranged. All five, indeed, agree in not having arillated seeds; but this, it is presumed, Willdenow himself cannotesteem a solid generic character, since, in the case of hordeum vulgare, and its variety, he does not allow it to form even a specific one. Mr. Haworth has therefore preferred keeping the genus, for the present, entire; but he thinks it may probably hereafter be divided into four at least. He has thrown them in the interim into two grand divisions, dearillata, arillate, and has subdivided them according to the difference of their leaves. The fourth dissertation is a new arrangement of the genus saxifraga, as far as it is cultivated in the British gardens. It extends to forty-nine species, fortyseven of which are growing in Mr. Haworth's collection, and twenty-six of them are natives of Great Britain: the other two, which he has not seen either living or dead,are taken up from the Hor tus Kewensis. They are arranged under the following sections: nudicaules, irregulares, ligulata, ciliatæ, lobatæ, and st lonifere. The second section contains only the well known anomalous s. sermentosa. Of the last three genera, generic and natural characters are given; but to the genus portulaca he has not ventured to assign an essential character. The fifth dissertation contains a description of twenty-four species which, as far as the author knows, have not been before described, viz.; three species of crassula, one of ornithogalum, four of narcissus, one of cotyledon, three of oxalis, four of euphorbia, one of sempervivum, six of cactus, and one of cacalia. All of them are now alive in his possession, except the ornithogalum, for a sight of which, in a living state, he is indebted to Mr. Whitley, of Brompton, who received roots of it from the Cape of Good Hope in 1803. The sixth and last dissertation consists of observations on several technical terms used by Linnæus, or others, in the science of botany, which are either obscure, and of difficult comprehension, or misapplied, or synonimous with others in actual use. Mr. Haworth gives us reason to expect, in a future publication, dissertations on the following subjects: 1. Aves Britannica, seu Synopsis avium Britannicarum, with remarks. 2. Reptilia Britannica, with remarks. 3. An account of the genus crassula, of the genus euphorbia, and the genus cactus, with de scriptions chiefly derived from living specimens in his own collection. We hope to be able in our next volume to announce their appearance. Original descriptions, with remarks, from so diligent and acute an observer, will always possess a sterling value. ART. VII. Flora Britannica. Auctore JACOBO EDVARDO SMITH, M. D. Societatis Linneana Preside. Imp. nat. Cur. Regia Londinensis. Holm. Upsal. Taurin. Olyssip. Phi ladelph.-Physiogr. Lund. Berolin, Paris. aliarumque societatum socio. 8vo. vol. 3. THE British naturalists, in general, and especially the lovers of botany, have great reason to congratulate each other on the singularly favourable combination of circumstances, which brought to this country the entire museum, and library, with all the MSS. of Linnæus. It is still more fortunate that they became the property of an ardent pursuer of natural science, who not only knows how to make good use of them himself, but takes a pleasure in permitting a liberal use of them to all who are engaged in the same studies. It was probably this auspicious acquisition, made at a critical time in the fervour of youth, which fixed the character of his mind, and rendered the object of his early predilection the chief employment of his life. Besides numerous other literary labours, in which it has |