49. 17 Dragon.

R. Asc. 16" 32. Decl. 53° 17′ N.

5th and 6th Mag.

Sir W. Herschel found the angle of position to be 24° S. Foll.; and, in 1819, Struve found it 26° 10′. The difference of right ascension was +0" 419; the difference of declination, 1" 85; and the distance 4" 19.

50. 43 Hercules. R. Asc. 16h 37'. Decl. 8° 55′ N.

4th-5th, and 9th-10th Mag.

Sir W. Herschel says that these stars are nearly of equal magnitude, and that the distance is about 12". M. Struve found, in 1819, that the difference of right ascension was -4" 15; the angle of position 39° 7′ S. preced.; whence the distance is 1′23′′.7, and the difference of declination, 53".5. If Sir W. Herschel observed the same star that Struve did, one of them must be variable, and their motion prodigiously great.

51. 46 Hercules. R. Asc. 16h 38'. Decl. 28° 42′ N.

6th-7th and 11th Mag.

Angle of position in 1783.1, 66° 36' S. Foll,

1802.7, 76 18

1819.7, 81 12

(To be continued.)

Herschel.

Ditto.

Struve.

ART. XV.-Observations on a new Natural Family of Plants, to be called Cobeacea*. By Mr DAVID DON, AssistantSecretary to the Linnean Society, Corresponding Member of the Wernerian Natural History Society, &c.

Ir not unfrequently happens that the most common plants:

are those which are the least understood, in a botanical point of view. The objects which have already become familiarized to our eyes seldom attract our attention, and the weeds which we trample under foot are heedlessly passed over as unworthy of our examination. These remarks are applicable to a great many of our most common plants, and to one of those, which I am about to describe, namely, Cobaa scandens, which adorns our garden

* Read before the Wernerian Natural History Society, 26th April 1823.

walls and arbours with its twining leafy branches and profusion of large blossoms. This graceful plant is a native of the Great Valley of Tenochtitlan, near the city of Mexico, and was first introduced into Europe in the year 1787, and, from its ready propagation, both by cuttings and seeds, has now become almost as common in our gardens as the ivy. The genus Cobaa was first described by the Abbé Cavanilles, in the first volume of his excellent work, entitled Icones Plantarum. Cavanilles has referred it to the Bignoniacea, and this arrangement has been followed by the greater part of botanists. A slight examination, however, will shew clearly that this view of the affinity of Cobra is extremely erroneous, and that its true place in the natural system has hitherto been entirely overlooked. The Genus, indeed, possesses almost no character in common with the Order in which it has had the misfortune to be placed by botanists. In order, however, to shew this more clearly, it will be necessary to state the great differences which exist between them. Cobau is distinguished from the Bignoniacea by a regular pentandrous corolla, by its long, simple, undivided, incumbent anthers, by a triple stigma, by the structure and form of its fruit, and by its nearly erect seeds, furnished with a fleshy albumen, and a simple covering. These characters bring it very near to the Polemoniacea, to which, of all established orders, it bears the strongest affinity, as M. Desfontaines has already suggested *; but it is abundantly distinct from these also, by the valves of the capsule being naked, and not. septiform, by the oblique position of the seeds, and by the habit of the plant itself. I therefore propose to form a distinct Order, to which the name of Cobeacea may be given. Cobra, the only known genus referable to it, has hitherto consisted of only a solitary species; but the extensive Herbarium of Aylmer Bourke Lambert, Esq., has enabled me to enrich it with a second species, collected by Don Juan Tafalla, a pupil of Ruiz, in the province of Quito, in Peru; and it is to be hoped that many new genera and species belonging to this Order still remain to be discovered in the extensive and little known re gions of South America.da

Ann. Mus. 2. p. 30,"

COBEACEÆ.

BIGNONIAC. pars, Juss. et Auctor.

Calyx foliaceus, 5-fidus, æqualis.

Corolla campanulata, limbo 5-loba, æqualis, æstivans imbricata. Stamina 5, fertilia, æqualia, exserta, basi cum corollæ tubo connata. Antheræ indivisæ, compressæ, biloculares, per medium filamentis incumbenti-adnatæ.

Ovarium simplex, triloculare: ovulis pluribus, adscendentibus. Stylus simplex. Stigma trifidum.

Capsula cucurbitacea, trilocularis, trivalvis: valvis crassissimis, intùs nudis. Septa nulla. Placenta maxima, centralis, trigona.

Semina plana, margine alata, duplici serie imbricata: testa simplex, superficie mucilaginosa: albumen carnosum.

Embryo rectus, foliaceus, incumbens: cotyledones cordatæ, inte græ: radicula infera, recta, centrifuga.

Frutices scandentes. Folia alterna, pinnata, apice cirrhifera. Flores axillares, solitarii.

OBS. Genus Cobææ adhuc Bignoniaceis malè associatum, nunc in novum ordinem constituere necessarium mihi videtur, quòd cum nullâ familiâ usque in serie naturali cognitâ, et minimè omnium cum Bignoniaceis convenit. Ab his longè discrepat corollâ regulari pen tandrâ, antheris indivisis incumbentibus, stigmate triplici, fructus formâ et structurâ, septis nullis, placentâ maximâ trigonâ, seminibus suberectis, testâ simplici mucilaginosâ, albuminis præsentiâ, cotyledonibus integris, radiculâ multò longiore; sed à Polemoniaceis, cui in multis accedit, tantùm triplici charactere, scilicet: seminibus adscendentibus, valvis capsulæ intùs nudis, septis nulis.

COBEA, Cavan. Juss.

Calyx maximus, foliaceus, quinquefidus, præfloratione quinquangulus: laciniis latis cordato-subrotundis lanceolatisve, marginibus inter se per paria arctè applicatis, hìnc calyx 5-alatus. Corolla ampla, campanulata, limbo 5-loba, æqualis lobis latè rotundatis margine tomento tenui vestitis; æstivantibus imbricatis, intùs prope basin coarctata atque lanâ molli niveâ copiosâ instructa. Stamina 5, æqualia, omnia fertilia, exserta: filamenta crassiuscula, teretia, apice attenuata, basi cum tubo corollæ connata, sed ferè totâ parte libera, erecta, distantia, nisi'ad bases, omninò glabra: antheræ magnæ, oblongæ, compressæ, indivisa, biloculares, per medium filamentis incumbentiadnatæ, apice obtusæ, basi latiore emarginatâ: loculi lineares, paralleli, singuli extùs rimâ longitudinali bivalvi dehiscentes, et pollen granulosum aureum effundentes. Ovarium oblongum, trigonum, basi disco magno nectarifero 5-angulo foveis 5 notato carnoso cinctum Stylus rectus, staminibus brevior, trisulcus. Stigma trifidum: laciniis linearibus, acutis, æqualibus, intùs planis. Capsula pyriformis, cucur bitacea, fructui Passiflora specierum quarundam omninò similis, trilocularis, trivalvis, sulcis 3 angulis placenta oppositis exarata: loculis oligospermis: valvis crassissimis, carnosis, marginibus appositis, me dio intùs nudis, ovali-oblongis. Placenta maxima, trigona, centralis

sed fructum omninò implens, carnosa, succulenta. Septa nulla nisi vestigia ferè obliterata, et in angulis placentæ immersa. latissima, compresso-plana, margine alata, duplici serie imbricata, adscendentia: testa simplex, tenera, crassiuscula, superficie densè mucilaginosa, lateris interioris prope basin hylo lineari-oblongo notata: albumen parcum, carnosum, lacteum, molle. Embryo magnus, rectus, incumbens, lacteus: cotyledones latæ, cordatæ, obtusæ, integræ, compressæ, applicata: radicula cylindracea, crassiuscula, cotyledonibus triplò brevior, infera, recta, basi obtusissima.

Frutices (Mexicani v. Peruviani) diffusi, ramosissimi, scandentes, glabri, frondosi, Passifloræ habitu similes. Folia tripari-pinnata, alterna, sessilia, apice terminata cirrho valido in spiram convoluto triplici v. quinque ordine dichotomo: foliolis integerrimis petiolulatis; infimis stipulas mentientibus. Flores magni, axillares, solitarii, pedunculati pedunculus medio bracteis 2 oppositis parvis impari-pinnatis præditus, sordidè purpurei fasciis albis notati aut lutei,

1. C. scandens, segmentis calycinis latè cordato-subrotundis, foliolis ellipticis mucronulatis.

Cobæa scandens, Cavan. Icon. 1. p. 11. t. 16. et 17. etiamque Vol. 5. p. 69. t. 500. Persoon Synop. 1. p. 185. Lam. Encyl. Suppl. 2. p. 305. Kunth in Nov. Gen. et Sp. Pl. 3. p. 151.

Hab. in Convalli Tenochitlensi prope urbem Mexico et ad Portum Acapulco Mexicanoruin. h. Vulgò dicitur Vedra Morada, id est, Hedera violacea.

2. C. lutea, segmentis calycinis lineari-lanceolatis mucronatis, foliolis oblongis acutis.

Cobæa macrostema, Pavon. MSS.

Hab. ad Portum Guayaquil in Regno Vuitensi Peruvianorum. Joannes Tafalla. h. (v. s. in Herb. Pavon. nunc in Mus. Lamb.) Præcedenti similis. Corolla lutea, minor. Stamina ultra limbum longè exserta. Stigmata longiora et angustiora. OBS. Nomen specificum Pavonii mutavi, quòd genere diverso minùs rectè cum regulis constitutis congruit

ART. XVI.-Observations on the Low Temperature of particular Cavernst.

IN endeavouring to account for the great cold which has been

observed in particular caverns, an explanation of this singular fact must be sought for, rather in local peculiarities than in relations of a more general nature. A phenomenon noticed by Professor Pictet, in the neighbourhood of one of those caves ‡,

• In addition to my observations on the genus Jacaranda, (see this Journal, Vol. IX. p. 264), I beg to add, that Mr Brown appears clearly to have been the first who has noticed the singular formation of the anthers in that genus.

+ These ingenious observations are taken by permission from the article PHYSICAL GEOGRAPHY in the Edinburgh Encyclopædia, which is on the eve of publication. They are necessary to complete the view of this interesting subject, which is given in this Journal, vol. viii. p. 1. 16.—ED.

See this Journal, vol. viii. p. 8.—ED.
2

is calculated to throw some light on the subject, though we are by no means disposed to admit that the conclusion he has drawn from it is altogether free from objection. At the ice-cave of Brezon, in the Alps, a current of cold air was observed to issue, with considerable force, from several crevices near the cavern, which depressed a thermometer exposed to its influence from 51° to 38°. In applying this fact to the solution of the cause of the phenomenon in question, M. Pictet cites the observations of Saussure on the air rushing from the cavities of Monte Testaceò, near Rome; where a little hill, composed of the fragments of urns, and other vases of earthen ware, produces an effect similar to that of the calcareous sides of these icy caverns. Round the base of this artificial mound several caves have been dug, in the back walls of which a number of perforations have been formed, running upwards like chimneys, and through which a current of cold air constantly descends in summer. On the 1st of July 1773, the external air being at 78°.1 Fahrenheit, the thermometer stood at 44° in one of the caverns, and at 44° in another. “It is certainly a very singular phenomenon,” says Saussure," that, in the middle of the Compagna of Rome, where the air is always burning-hot and suffocating, there should be found a little insulated hill, from the base of which should issue, on all sides, currents of air of an extreme coolness." Saussure mentions several other places, where he observed that a current of air rushing from crevices in the rocks, which formed the sides of caves, was accompanied with a great degree of cold. The caverns in which the cold was the most remarkable, were generally situated in calcareous rocks, at the foot of a mountain. In short, these grottoes appear, in many instances, to be the mouths of natural galleries, communicating with upright shafts, through which a stream of air flows downward, when the temperature of the external air exceeds that of the cavern. The current of air thus determined, must acquire, during its descent, the temperature of the vertical portion of the crevices through which it passes; and that temperature must in general be at least as low as the mean temperature of the place. Professor Pictet supposes that the air descending through these fissures in the strata must be still further cooled by the refrigerating effect of evaporation, from the moistened materials which it encounters in its progress; VOL. X. NO. 19. JAN. 1824.

H