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the quantity absorbed. For, it would appear, according to Sir Issac Newton's experiments, that, at an angle of 42° of incidence (48° from the perpendicular), only from one-thirtieth to one-fortieth part of the light impinging is reflected from water. Is this proportion of light, then, sufficient for the production of the iris ? There is good reason to suppose, I conceive, that even this proportion is abundantly adequate to the production of the phenomenon, because the light of the full-moon is occasionally sufficient for the purpose ; yet that light, according to Dr Smith,. is little more than a ninety-thousandth part of the light of the sun, or, according to M. Bouquer, not above a three-hundredthousandth part. In either case we see, that the light reflected from the sea, when the sun has an altitude of 42°, is some thousands of times greater than the quantity which is sufficient for the production of the lunar iris; consequently we may infer that an inverted iris from the reflected

rays
of the

sun, may occur even when the sun has the greatest altitude to which it ever attains in any temperate or frigid climate

This being the case, there seems to be reasonable ground for supposing, that the reflection of the sun's rays from a perfectly calm surface of water, may have a share also in the production of some of the various phenomena of haloes, such as are not otherwise explained,-a supposition which the resemblance that figures 2 and 3 bear to some of the prismatic circles, renders more than probable.

Tour to the South of France and the Pyrenees, in 1825. By

G. A. WALKER Arnott, Esq. A.M. F.L.S. & R.S. E. &c. In a Letter to Professor JAMESON. (Continued from the

preceding Volume, p. 275.) I

HAVE taken notice of the Capouladoux Cyclamen, because by some it is considered as very different from the C. hederæfolium. The Montpellier' plant is certainly the same as that found in Corsica, and I believe not unfrequently along the shores of the Mediterranean. It flowers in spring. In this respect it agrees with that said to be found wild in Britain, but which has probably escaped from some garden. I have never seen the

latter, but by the description given by Sir James Smith, it appears to differ in the leaf. The English plant has the leaves " angular and finely toothed," and agrees in that respect with the character given by Roemer and Schultes. The Montpellier and Corsican species has the leaf much angled, but otherwise very entire. The nerves, however, at the angles, and here and there along the margin, project, and form each a small callous point. Whether or not this be considered a good distinctive character, the C. neopolitanum of Tenore is certainly different from either : this last flowers in autumn, and the petals are much shorter, and more obtuse *

On the 14th April we went before breakfast to Mirval. Here there is a cavern, into which one is obliged to enter on all fours; but it soon becomes very spacious. In it there is said to be (for our time scarcely permitted us to enter, and we were unprovided with torches) a great body of water: it is by many supposed to be the source of a pretty large stream, which does not make its appearance for a considerable distance. Theligonum cynocrambe, Lavatera maritima, Gouan, (a plant much confused with L. Ol bia), Asplenium glandulosum (the two last remarkably scarce), Linaria simplex, Lathyrus setifolius, Fumaria "capreolata (a distinct and much more beautiful species than that of Britain, which is thé F. media of De Candolle, and perhaps only a variety of F. officinalis), Cneorum tricoccum, gigantic specimens of Clypeola jonthlaspi, &c. rewarded us for our morning's drive. We had gone with M. Bouchet in his carriage, and he saved us much time, as he had frequently herborized here himself, and knew the localities. M. Bouchet's herbarium is perhaps the best in the south of France. Among other rarities, it contains specimens of all the plants collected by Broussonet in the north of Africa and the Canary Isles.

* On the Pic St Loup, on some stones under the brushwood, we found Hypnum tenellum, whilst at Vaucluse we met with a moss which in some things so resembles this species, that I felt undecided whether or not to pro, nounce it distinct, unless I had compared it with what I consider the true H. tenellum. Its occurrence on the Pic de Loup enabled me, I think, to state decidedly that the two are very different. That found at Vaucluse has been also discovered by M. Requien in several other localities about Avignon, and Bridel has given it the name of Hypnum laxepennatum in Requien's herbarium. I suspect, notwithstanding, that it is a species formerly collected by Bridel at Rome, and already named by him in his Species Muscorum, P. ii. p. 111. Hyp. curvisetum. He, however, describes the leaves as subserrate, whereas in our plant they are entire: he considers his as a variety of H. Scleicheri (betwixt which, again, and H. confertum, I can find no good difference); but ours differs, by the scabrous seta, and entire leaf. The character I propose is as follows: H. curvisetum. Caule vage ramoso, foliis ovato-acuminatis integerrimis e stri

atis, nervo supra medium evanescente, theca globosa subcernuata (v. po

tius æquali nutante), operculo rostrato, seta grosse muriculata. Peristomium internum cilios inter lacinis habet : habitu multum refert H. te

nellum, at foliis latioribus, et seta valde differt ; refert etiam H. confer. tum, at differt seta muricata breviori, et foliis integerrimis.

On the 15th, we botanized towards Pont Juvenal, where we found a few rare native plants. Nearly all, however, that are found here, ought to be received cum nota. Every year a great quantity of wool is brought from Africa : it is-landed at Pont Juvenal (called also Port Juvenal, for vessels come up this length to unload), and is spread out here to be bleached. Not a few seeds of African plants remain attached to the wool, and are thus sown; and the following year, when the ground for the wool is changed, they spring up. M. Delile, by searching diligently every fortnight or three weeks, has been so fortunate as to meet with several plants naturalized no where else in Europe, and some of them scarcely at all known to the botanist. We did not observe any of them. These plants ought not to be admitted into the French Flora, but ought to constitute a separate one, this spot being actually a wild garden. Notwithstanding, I fear that Stipa micrantha, Desf. Psoralea palæstina *, and several others, are no where else found in France.

Up to this period (the 15th), we had kept no account of what we dried ; but as by this time I had agreed to give up Switzerland, and go to the Pyrenees, where we intended to keep a catalogue of every plant we collected, we considered it better to habituate ourselves to that labour. Hitherto we had dried probably not more than 1500 or 2000 specimens ; but that may be reckoned a great number, when we consider the early season of the

* Mr Bentham and I afterwards discovered St. micrantha on the Spanish side of the Pyrenees, where it was certainly wild, but exceedingly scarce. That is, as far as I know, the only locality in Europe where it is absque dubio indigenous. As to Psoralea palæstina, it was not sufficiently advanced when I was at Pont Juvenal for me to judge of it in the live state; but the dried spe. cimen exhibits not one specific character that I can see between it and Ps. bituminosa, which is exceedingly common in the south of France. Is it to the nose, and not the eye, that we should trust for the distinction ?

year. 22d April.—In company with Delile and Dunal, we botanized to-day for a few hours about Restinclières : we now found several Helianthema in flower. Polygala monspeliaca was beginning to make its appearance, at least we only met with a very few specimens. Euphorbia segetalis, sylvatica, characias, and several other species, have been in flower for some time, but they are so troublesome to dry, that we have looked forward to that task with little pleasure. At first they were not in fruit, and now other plants are in abundance : to-day, however, we dried a few of Euphorbia rubra and retusa (my distinguished friend M. Roeper has, with great justice, re-united these to E. exigua): Fedia auriculata we also met with. M. Dunal, with a liberality of mind that distinguishes every true botanist, from the observations he made to-day, avowed that he now considers the Helianthemum apenninum is not distinguishable from H. hispidum: to these may perhaps be joined H. virgatum. Helianthemum canum and penicellatum are two species very common here. I never heard of the latter before rival at Montpellier; and I doubt extremely if I shall ever be able to distinguish it, unless assured that the specimens before me come from the midi de la France. How to separate it from the H. alpestre, or even from H. ælandicum, requires a nicer eye for discrimination than I possess. The most serious characters are, that in H. ælandicum the flowers are said to be small, and the leaves nearly smooth. This, however, is at best a contested species. I am willing to consider it as an accidental variety; but I cannot believe that the small size of the flower is constant, or ought to form a reason for distinguishing it

specifically even although such had ever been observed. In H. alpestre, the flowers are large, the leaves various, smooth, carnose, or hirsute; while in H. penicellatum the leaves and the sepals are more pilose. These three, I conceive, may prudently be united, and to them be added H. obovatum. The characters to separate these from H. canum are more easily perceived: in the preceding, the leaves, though covered with hairs, are neverthe

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less green ; while in H. canum, they are white and hoary. But what, then, becomes of the intermediate H. italicum, which

partakes of both these characters * ?

“ Of Helianthemum fumama and procumbens we also laid up a few specimens to-day. Dunal is certainly right when he adds the remark, that perhaps H. ericoides is but a variety of H. fumama : it is no doubt a very distinct variety, but has no claims to be ranked as a species, nor does it appear to differ in the least degree from var. a of H. fumama: may not even var. be joined to var. «? Further, on what good grounds is H. pro cumbens to be separated ? Dunal rests upon the property of the seeds f remaining attached to, or being discharged from the opened capsule; but we have assuredly found both on the same plant, and as to habit there is little difference.

“ Few who find Cisti and Helianthema together in the wild state, would, I think, presume to unite the two genera ; yet there does exist a species which tends to ally them most intimately. I allude to the old Cistus libanotis. Now, it is difficult to say to which genus this should be referred, by judging only of the habit. Nay, there seem to have been two distinct species confounded together, but which Dunal has properly separated: the one has the capsule of a Cistus, the other of a Helianthemum ; they differ in no other respect. Dunal has called the one C. Clusii, the other Helianthemum libanotis. In both, the styles are shorter than the stamina, and the calyx trisepalous. To H. libanotis, Dun. certainly belongs Cistus calycinus, Linn. This synonym is adduced by Willdenow under

# The Helianthemum canum, Dun. I believe to be the C. canus of Linnæus ; but Sir J. Smith says that Linnæus's plant is very different from his C. mari. folius, whereas Dunal's H. canum is so closely allied to it, that there is scarce. ly either a natural or artificial character by which it is to be separated. As to Dunal's H. marifolium, it certainly differs from the British C. marifolius, with which, however, De Candolle's plant (from Switzerland) entirely accords. There are thus three species : Hel. canum of Dunal and Linn.; H. marifolium, DC. and Linn.; and Dunal's H. marifolium.

1

+ My friend M. Guillemin has recently discovered, that, in the end of the broad and narrowed Helianthemum, there exists two different structures of the embryo.

JANUARY-MARCH 1827.

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