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Hawaian Islands, which were visited in 1840. The Polypetalæ were published in full in the Botany of the Expedition by Gray, who has also published new species of Monopetalæ in Vols. IV., V., and VI. of the Proceedings of this Academy. But few of the Apetalæ have yet been noticed. The Ferns, by Brackenridge, were published as a separate volume of the Botany of the Expedition; but nearly the whole of the edition was destroyed by fire. Another partially published volume comprises the Mosses by Sullivant, the Lichens by Tuckerman, and the Algæ by the late Professors Bailey and Harvey.

Nuttall visited the Islands in 1835, from the Northwest Coast, and made a small collection. Most of his specimens are in the Hookerian Herbarium; a few probably in that of the Philadelphia Academy. He published notes and descriptions of some Hawaian Compositæ, Lobeliaceæ, and Vaccinieæ in the Transactions of the American Philosophical Society.

JULES REMY went to the Islands under the auspices of the Paris Museum, and made a fine collection in the years 1851 - 1855.

Wm. HILLEBRAND, a physician resident in Honolulu, has recently sent interesting collections to Kew, among them a new genus of Begoniacee, which Prof. Oliver has named after its discoverer.

W. T. BRIGHAM, with whom I visited the Islands, aided me constantly in collecting, and remained five months after my return, obtaining several species not in my own collection.

The Hawaian Islands lie just within the northern tropic, between 18° 55' and 22° 20' N., and 154° 50' and 160° 40' W. Their climate is not extreme, being much moderated by the N. E. trade winds, which blow pretty steadily for three fourths of the year. The mean annual temperature at Honolulu is about 79° Fahr.; that of the summer, or from May to October, about 81°, and that of the remaining half-year, or winter months, about 75° ; the thermometer ranging mostly between 60° and 86o. Labaina, under the lee of the mountain of West Maui, and Waimea, in the same relative position to the mountain of Kauai, are the two hottest places, while on the summits of the highest mountains the snow persists through nearly the whole year. The snow descends on the flanks of the high mountains to a level of 6,000 or 7,000 feet above the sea, at least in cold winters, but never lies at that elevation long, quickly retreating upward with the return of a warm day.

VOL. VII.

19.

The group comprises thirteen islands, only seven of which, however, are of any considerable size. These extend in a curved line from E. S. E. to W. N. W., about 600 miles in length. Their superficial area is about 6,500 square miles; the largest island, which is also the most easterly one, Hawaii, being about 100 miles long, by 80 or 90 miles wide, of an irregular oval shape. It also presents the highest mountains of the group, as well as of the Pacific, — Mauna Kea being 13,980 feet, and Mauna Loa, 13,760 feet; Hualalai somewhat exceeds 8,000 feet.

The next island to the west, Maui, is the next in size also. It consists in fact of two islands, joined by a low sandy isthmus, so low that more than one vessel has been wrecked by attempting to pass between them, mistaking the gap for the Molokai Passage, next westward. The eastern end of Maui is composed of the mountain Haleakala, somewhat exceeding 10,000 feet in height. West Maui is about 6,500 feet high; its mountain is known as Eeka; several of its highest portions also bear distinctive appellations.

Molokai lies next to the westward, but is the fifth in size. The highest point is near the eastern end, and perhaps reaches 3,500 feet.

Lanai lies a few miles S. S. W. from West Maui, and is the sixth in size. It probably does not exceed 2,500 feet in height.

Oahu, west of Molokai, is the fourth in size. Its mountains are two somewhat parallel ridges of unequal length, lying nearly east and west, the northern one twice the length of the southern. The northern ridge is partly divided by Nuuanu Valley, the mountains to the east taking the name of their highest peak, Konahuanui; those to the west, the name of Waiolani, the highest peak on that side. Each of these peaks probably a little exceeds 4,000 feet. The farther western end of this range (sometimes called the Waialua Mountains) spreads out to a very considerable breadth, and is extremely difficult of access, so much so that it is probable no white man has ever been to the heart of the region. The southern ridge is known as the Kaala Mountains.

Kauai, the island next west, is the third in size, consisting in great part of a central mountain, 6,500 or 7,000 feet high, with an extensive plateau on its leeward flank, at the height of from 3,000 to 4,000 feet.

Niihau, the most westerly island (excepting a few mere rocks) lies to the S. W. of Kauai, is the seventh as regards size, is in no part above 2,500 feet, and is destitute of forests.

Returning again to Hawaii, where on the whole the climatic condi

tions are the plainest, and the regions of vegetation best defined, we have an island whose shores are the lower slopes of three mountains, the relative position of which is that of the three angles of a nearly equilateral triangle. These mountains enclose an extensive plateau at an elevation of about 5,000 feet. The windward shores and slopes of Hawaii are the most rainy part of the group, in consequence of the high peaks above, which condense the moisture of the trade winds, and keep it almost continually falling. The elevated plateau is dry, as much on account of its sterility, as it is sterile on account of its dryness; for whatever rain reaches it sinks into the porous lava soil as fast as it falls. The low region is comparatively sterile on account of its being cut off by the high intervening peaks from the reach of the trade winds, and its heat quickly evaporates any thin clouds which may drift over it. The higher leeward regions possess of themselves sufficient coolness to condense the moisture of the air into clouds; and it is owing to the protecting influence of the mountain peaks that the clouds are not blown away by the strong trade winds before they deposit their moisture, as is the case in some places. Thus we have a wet region all along the eastern side of the island, and extending around to the south and to the west, until it reaches the base of Hualalai ; and this wet region, between the height of 1,500 or 2,000 feet to about 5,000 feet, is the most heavily wooded of the group. The parts between 1,500 feet and the sea level comprise comparatively few species, and but little of the peculiar vegetation. The high and dry mountain tracts, above 4,000 or 4,500 feet, are very distinct in their character and vegetation from either of the regions below. The highest lava summits are nearly destitute of vegetation.

Similar considerations, making allowances for physical contour, &c., explain the similar distribution of wet and dry regions, and of vegetation, on the other islands. Thus, the summit of Haleakala, above 6,000 feet, has the character and nearly the same plants as the higher parts of Hawaii, and its windward slopes are wet and heavily wooded. The high summit stands in the way of the winds in such a manner as to make an eddy to the leeward, where clouds gather every day, and supply sufficient moisture to sustain a forest, while other parts are more frequently cloudless and drier. The summits of West Maui, Oahu, and Kauai, lying between the heights of 4,000 and 6,500 feet, are just in the cloud level, and, being also peaks where denudation has long been active, the soil bas become somewhat impervious to moisture, which

therefore remains on the surface. The region has a peculiar aspect, which is at once recognized in ascending the mountains. The only forest-tree, the ohia lehua (Metrosideros polymorpha) becomes stunted; the trunks are covered with a thick coating of Mosses and Hepatice, which retains the moisture so as to render everything dripping wet; and not more than a dozen species of flowering plants and ferns occur in the whole. Above this, on the mountains of West Maui and Kauai, there is an open tract, where the lehua, one of the largest forest-trees, at an elevation of 2,000 feet, has become dwarfed, a foot or two high, in spreading clumps, but still flowering luxuriantly. In the midst of such clumps are found the violets peculiar to these regions, and in the neighboring tussocks of sedge (an Oreobolus) are found the few other plants, which occur here and nowhere else, to the number of eight or nine; also Drosera longifolia, thousands of miles from its next nearest known habitat.

The lower parts of the Kaala mountains, and the lower parts of the leeward flank of Kauai, have many characteristics in common, both being somewhat deprived of moisture by high land to the windward.

By far the greater portion of the soil has been formed by disintegration of the lava; the thin sandy soil of those parts which consist of raised coral reefs (as some of the shore regions of Oahu), and that which is formed by the drifting inland of the calcareous beach sands, support a few species which are not found elsewhere.

It is the purpose of this enumeration to give as complete a list as possible of the plants indigenous to the group, inserting also the probably introduced plants which have become thoroughly naturalized. Those which are without doubt indigenous have been left unmarked. Those which are probably of aboriginal introduction are marked with an asterisk (*); the few which are in all probability recent introductions, with a dagger (†).

The specimens which have been distributed, under numbers, from the collection of Mr. Brigham and myself, are referred to by the initials M. & B. The numbers of Remy's plants are cited, as far as they have been met with in the Gray Herbarium. Hillebrand's collection is not here represented fully enough to make it worth while ordinarily to cite his numbers.

Ranunculacea. 1. RANUNCULUS HAWAIENSIS, Gray, Bot. S. Pacif. Expl. Exp. 1, p. 10. (M. & B. 314.)

2. RANUNCULUS MAVIENSIS, Gray, l. C. p. 11, & var. B. (M. & B. 446; Remy, 920.)

Menispermacea. 3. Cocculus FERRANDIANUS, Gaud. Bot. Voy. Freyc. p. 477, t. 101; Walpers, Rel. Meyen. p. 298. Nephroica Ferrandiana, Gray, Bot. S. Pacif. Expl. Exp. 1, p. 39. (M. & B. 110.)

Cruciferæ. 4. CARDAMINE HIRSUTA, Linn.; Gray, Bot. S. Pacif. Expl. Exp. 1, p. 50. (M. & B. 311.)

5. LEPIDIUM OWANIENSE, Cham. & Schlect. in Linnæa, 1, p. 23 ; Hook. & Arn. Bot. Beech. Voy. p. 78; Walp. Rel. Meyen. p. 250 ; Gray, l. c. p. 63. The cotyledons, at least in some seeds, are accumbent. (M. & B. 343, 593; Remy, 523, 524.)

6. LEPIDIUM SERRA (sp. nov.): fruticosum, fere glabrum ; foliis lanceolatis crebre arguteque laciniato-serratis membranaceis ad apicem ramorum confertis inferne in petiolum gracilem longe attenuatis ; pedunculis gracillimis folia subsuperantibus racemos breves corymbosos bracteis filiformibus stipatos gerentibus ; floribus longe pedicellatis ; siliculis junioribus ovato-rhomboideis stylo apiculatis, maturis oblatoorbiculatis, stylo ex emarginatura minima vix exserto; cotyledonibus accumbentibus. — Hanapepe, Kauai. — A straggling, much branched shrub, 2 - 3 feet high. The young inflorescence is slightly puberulent. The cotyledons are clearly accumbent! (M. & B. 588.)

7.1 SENEBIERA DIDYMA, Pers. Ench. 2, p. 185; Desv. Journ. Bot. 3, p. 164; Gray, l. c. p. 63.

Capparidacea. 8. CLEOME SANDWICENSIS, Gray, Bot. S. Pacif. Expl. Exp. 1, p. 65. Cleome spinosa, Hook. & Arn. Bot. Beech. Voy. p. 78; Walp. Rel. Meyen. p. 251, non Linn.

9. CAPPARIS SANDWICHIANA, DC. Prodr. 1, p. 245; Hook. & Arn. Bot. Beech. Voy. p. 59; Gaud. Bot. Voy. Bonite, t. 55; Gray, l. c. p. 69. (M. & B. 108; Remy, 529.)

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