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This is called "Shirwa," and reaches to the north for at least 50 or 60 miles, being separated there from the "Ninyessi," by a piece of flat land, not many miles across. We waded in until the water reached our waists, in hopes of reaching a point whence we could take observations on the sea horizon, but the grass and reeds extended still farther, and we had to return covered with leeches. We had for guides then some of the slave party, and the people of the country said that they had led us off the proper path which goes to the bank in order to drown us. However, we got back all right; and that evening found it was in lat. 15° 23′ and long. 35° 35'. Having now seen this great lake, we thought we could not do much more at present. Here was a navigable inland sea, leading up to the great lake, of which rumours have for long reached us, and for which Captain Burton is now in search. We were rather anxious, too, for those in the vessel which we had left in the Shire, under the Quarter-master and Second Engineer, who were acting alone this trip.

On our return, we followed a different route, which took us over a high plateau, between 3000 and 4000 feet (the lake was 1800 feet above the Shire). This elevated region came down near to the Shire, and we found the path much easier than that by following up the river.

This seems to be a healthy part. We were out 23 days, and very seldom slept under cover; we were wet every morning with dew, and our clothes dried as we marched in the burning sun. Yet we were never delayed a day by the sickness of any one of the party, although often fatigued by evening with the heat and heavy road. The marches appear short when we came to correct them by observation; but they generally took us from sunrise to sunset, with only an hour to breakfast, and a rest of a few minutes about noon.

As to the geology of the country, it is all schist rocks, with a few spots of trap and porphyry. The strike is north and south. There is abundance of iron ore, which the natives reduce for knives, spears, and arrow heads. They also trade in hoes for cultivating the soil, with the neighbouring tribes.

The people are all "Manganja;" speak a modification of the language of Tette and Senna. The women are distinguished by the most repulsive of savage ornaments, a ring of ivory or bamboo, like a ring for a table napkin, in the upper lip; the lip being distended round the circumference, and projecting like a duck's bill.

Their religion is pure deism; they believe in a god and in medicine, or the ordeal which he directs as the means of discovering crime; if it cause vomiting, it shows innocence; if it acts by the bowels, crime, and they are put to death. But the doctors have a good knowledge of which to give, for there are different plants used. The only thing coming near to an idol which we heard of was the keeping the soul of their father in a basket, which they bring out when they get drunk with beer; but we could never get them to show it to us. When dead, they turn to lions and other beasts; only witches are made into crocodiles.

On our return, the Quartermaster was sick, but beginning to recover; he had been down with fever ever since we left. He is now better.

We are on our way to the mouth of the river to meet a man-of-war, with stores. We hear that the party at Tette have had a good deal of sickness; but the unhealthy season is quickly passing.

Daily exercise is absolutely necessary for health out here.

Dr. Livingstone and I have had fortunate health all along, although constantly in the most malarious districts, such as the Mangrove swamps of the Suabo, or the low lands of Senna and marshes of the Shire; out the whole day in the sun or rain. I believe the exercise more than counterbalances all these. One day when exposed to the sun, dissecting a young elephant, I found I could not stand it at all; had I been working I should not have felt it.

We are not without our own politics here, even in this outlandish place. The slave-trade goes on briskly from one of the mouths near Quillimane, to supply the demand at Bourbon. Those in power being of the French party, wink at it. The authorities are poorly paid, and have to make it up by other means. Trade is difficult; they lay themselves out for nothing but ivory and gold. They might have cotton and sugar, and that without the use of guano, as is required in Mauritius, and by the very hands they ship off to the French. The whole of Suabo, at the mouth of the river, is splendid cotton and cane land, and in the hands of the Portuguese. Those up the Shire are quite beyond their power; and even at Shupenya, near Senna, they have to pay tribute to the Landeens. They have last autumn finished the war with Mariano, who set himself up as independent; but there is still a great robber within a few miles of the town of Tette, which every canoe must pass on its way to Quillimane. We expect the Governor-General of the Province here immediately; he comes to establish his brother at Tette, as Governor of a new district which they call Zambezia, and which was formerly under that of Quillimane. We shall feel the want of Senhor Tito, the former commandant, who ought to have been mad governor; he is the best man for it. We shall have to change our quarters, being at present established in the Residency at Tette.

2. On the Morphological Import of Certain Vegetable Organs. By CHRISTOPHER DRESSER, Ph.D.

The author gave the results of his investigations into the morphological import of certain vegetable structures, especially those entering into the composition of the flower.

He commences his argument by contending that bud-scales, or Perulæ, are in many instances not metamorphosed leaves, but merely flattened petioles. He appeals to examples in Acer and Esculus, where not unfrequently the bud-scales are furnished with small laminæ at their extremity, while they themselves remain unaltered. This proves, he considers, that the bud scales are not metamorphosed or rudimentary entire leaves, but only represent petioles.

The tubercular papilla at the point of the normal bud scale, and which is the first part that appears in its development, suffers what he terms a quasi-paralysis, or arrest of development; while, in the abnormal examples cited, this arrest does not take place, but the papilla proceeds to be developed into a lamina, as in the true leaf-the so-called transmutaion in these instances resulting only from a more or less complete evolution of this papilla.

The author then endeavours to prove that the Calyx, in many instances, is a whorl of petioles-laminæ, in these cases, not entering into its com

position. He refers, 1st, to the calyx of lavender, where one of the sepals develops a little lamina, which is more or less completely articulated to it; 2d, to the calyx of Mussanda macrophylla, where one sepal develops a lamina, while the other sepals, which are normal, are precisely parallel to the petiolar portion of the developed one; and lastly, to the monstrous calyx of a rose (which was exhibited), where from the sides and apex of the sepals, leaflets in various states of development were seen to spring, while the sepals themselves retained more or less completely their flat, phyllous, and conical normal form; in this instance the sepals are not transmuted into true leaves, but leaflets are developed upon their sides. This mode of reasoning is the same as that by which the Phyllodium of the acacia is universally regarded as a leaf-stalk, simply because a compound leaf is sometimes emitted from its apex.

Regarding Petals, the author adduces the following:— that petals continually become sepals in monstrous flowers, and this most commonly in flowers whose sepals have most manifestly a petiolar origin, as in roses; again, that in the Caryophyllacea flowers occur having petals with the most fully developed and clearly defined claws and limbs, while in those plants the leaves are so constantly sessile as to afford a characteristic of the race. From these circumstances he infers that in some cases, probably in roses, the petals result from petioles; whereas in other cases (as in the Caryophyllaceae) they result from entire leaves. He does not, however, consider that, in these latter plants, the claws and limbs of the petals correspond to petioles and laminæ. "It seems contrary to reason to suppose that all the normal leaves of the plant should be sessile, as well as the leaves composing the outer floral envelope (the sepals); whereas the members of the inner floral envelope (the petals) should be raised upon long stalks."

Regarding the Stamens, the author urges arguments similar to those applied to the petals. The stamens may pass through the stages of petals and sepals, so "that whatever is the nature of the petal, such is the nature of the stamen also." Moreover, that in those plants with sessile leaves, the filaments and anther cannot correspond to petiole and lamina. He also refers to a monstrous stamen of Tradescantia virginica, where one-half of the stamen is converted into a petaloid member, which extends from the base of the filament to the summit of the anther, indicating that here the whole stamen corresponds to the sessile petal, and that there is thus no distinction, in this case, into petiole and lamina.

The author inclines to the belief that the carpel is in some cases equivalent to a petiole, from the fact that in certain cases monstrous carpels develop their ovules into rudimentary leaves. He does not, however, insist strongly upon this point, since he does not think it yet proved that ovules may not be true buds.

Sir Thomas Buchan Hepburn, in a letter to Dr Balfour, called attention to the mode in which Taxodium sempervirens sheds its leaves. The leaves themselves do not fall, but the small branchlets drop off, as if each branchlet was a pinnate leaf. Specimens were sent to illustrate this fact. The tree from which the specimens were taken was planted at Smeaton, a small seedling, in 1844, and is now about 28 or 29 feet high. Its mean annual growth for the last eight years, up to December 1858, has been about 2 feet 4 inches. It has not yet flowered.

157

SCIENTIFIC INTELLIGENCE.

BOTANY.

Distribution of Vegetable Species. By Professor ASA GRAY.—A review of what has been published upon the subject of late years makes it clear that the doctrine of the local origin of vegetable species has been more and more accepted, although, during the same period, species have been shown to be much more widely dispersed than was formerly supposed. Facts of the latter kind, and the conclusions to which they point, have been most largely and cogently brought out by Dr Hooker, and are among the very important general results of his extensive investigations. And the best evidence of the preponderance of the theory of the local origin of species, notwithstanding the great increase of facts which at first would seem to tell the other way, is furnished by the works of the present De Candolle upon geographical botany. This careful and conscientious investigator formerly adopted and strenuously maintained Schouw's hypothesis of the double or multiple origin of species. But in his great work, the Géographie Botanique Raisonnée, published in the year 1855, he has in effect discarded it, and this not from any theoretical objections to that view, but because he found it no longer needed to account for the general facts of distribution. This appears from his qualified, though dubious, adherence to the hypothesis of a double origin, as a dernier ressort, in the few and extraordinary cases which he could hardly explain in any other way. His decisive instance, indeed, is the occurrence of the Eastern American Phryma leptostachya in the Himalaya Mountains. *

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I know not whether any botanist continues to maintain Schouw's hypothesis. But its elements have been developed into a different and more comprehensive doctrine, that of Agassiz, which should now be contemplated. It may be denominated the autochthonal hypothesis.

In place of the ordinary conception, that each species originated in a local area, whence it has been diffused, according to circumstances, over more or less broad tracts-in some cases becoming widely discontinuous in area through climatic or other physical changes operating during a long period of time-Professor Agassiz maintains, substantially, that each species originated where it now occurs, probably in as great a number of individuals occupying as large an area, and generally the same area, or the same discontinuous areas, as at the present time.

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This hypothesis is more difficult to test, because more ideal than any other. It might suffice for the present purpose to remark, that, in referring the actual distribution, no less than the origin of existing species, to the Divine will, it would remove the whole question out of the field of inductive science. Regarded as a philosophical question, Maupertuis's well-known "principle of least action" might be legitimately urged against it, namely, "that it is inconsistent with our idea of Divine wisdom, that the Creator should use more power than was necessary to accomplish a given end." This philosophical principle holds so strictly true in all the mechanical adaptations of the universe, as Professor Pierce has shown, that we cannot think it inapplicable to the

organic world also, and especially to the creation of beings endowed with such enormous multiplying power, and such means and facilities for dissemination, as most plants and animals. Why, then, should we suppose the Creator to do that supernaturally which would be naturally effected by the very instrumentalities which he has set in operation?

Viewed, however, simply in its scientific applications to the question under consideration (the distribution of plants in the temperate zone of the northern hemisphere), the autochthonal hypothesis might be tested by inquiring whether the primitive or earliest range of our species could possibly have remained unaffected by the serious and prolonged climatic vicissitudes to which they must needs have been subject; and whether these vicissitudes, and their natural consequences, may not suffice to explain the partial intermingling of the floras of North America and Northern Asia, upon the supposition of the local origin of each species. Let us bring to the inquiry the considerations which Mr Darwin first brought to bear upon such questions, and which have been systematically developed and applied by the late Edward Forbes, by Dr Hooker, and by Alphonse De Candolle.

No one now supposes that the existing species of plants are of recent creation, or that their present distribution is the result of a few thousand years. Various lines of evidence conspire to show that the time which has elapsed since the close of the tertiary period covers an immense number of years; and that our existing flora may in part date from the tertiary period itself. It is now generally admitted that above 20 per cent. of the mollusca of the middle tertiary (Miocene epoch), and 40 per cent. of the pliocene species on the Atlantic coast still exist; and it is altogether probable that as large a portion of the vegetation may be of equal antiquity. From the nature of the case, the direct evidence as respects the flora could not be expected to be equally abundant. Still, although the fossil plants of the tertiary and the post-tertiary of North America have only now begun to be studied, the needful evidence is not wanting.

On our north-western coast, in the miocene of Vancouver's Island, among a singular mixture of species referable to Salix, Populus, Quercus, Planera, Diospyros, Salisburia, Ficus, Cinnamomum, Persoonia, or other Proteacea, and a Palm (the latter genera decisively indicating a tropical or subtropical climate), Mr Lesquereux has identified one existing species, a true characteristic of the same region ten or fifteen degrees farther south, viz., the Redwood or Sequoia sempervirens. In beds at Somerville referred to the lower or middle pliocene by Mr Lesquereux, this botanist has recently identified the leaves of Persea Carolinensis, Prunus Caroliniana, and Quercus myrtifolia, now inhabiting the warm sea coast and islands of the Southern States.*

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At length, as the post-tertiary opened, the glacier epoch came slowly on-an extraordinary refrigeration of the northern hemisphere, in the course of ages carrying glacial ice and arctic climate down nearly to the latitude of the Ohio. The change was evidently so gradual that it did not destroy the temperate flora, at least not those enumerated as ex

*These and other data, obligingly communicated by Mr Lesquereux, have been published in the May number of the American Journal of Science and Arts for 1859.

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