arc of the coil last formed will exhibit a gradual fading-off of light towards its extremity. Mr. Proctor has calculated that a star ten times as far off as a Centauri, and having a real diameter as large as our sun's, would give an arc of fading light about 56 degrees in length. 4. BOTANY. Edible Fungi.-During the last few years great attention has been paid by botanists on the one hand, and epicures on the other, to the edible qualities of certain fungi. Notwithstanding the prejudice generally entertained against this class of vegetable productions, extending in Scotland, Wales, and some parts of England even to the common mushroom, there is no question that a considerable number of species, very abundant in this country, are not only wholesome, but delicious articles of diet, and are at least as easily distinguished, with a little practice, from the poisonous or suspicious species, as berries or other wild fruits. Containing a larger proportion of nitrogen than any other family of the vegetable kingdom, they furnish an abundant supply of nourishment at a period of the year when very little else is to be obtained. It is calculated that there is scarcely a parish in England where tons of wholesome food are not allowed to waste every year, to say nothing of the facilities for their artificial culture. Mr. Berkeley reckons that there are at least 30 distinct English edible fungi; Dr. Curtis has partaken of 40 in North Carolina, and enumerates 111 species in that state alone reputed to be edible. Fries, the greatest living cryptogamist,. is publishing a large work on the edible and poisonous fungi of Sweden; several works of a similar character have recently been brought out in Italy; in our own country the Rev. M. J. Berkeley, Mr. Worthington G. Smith, and Dr. Bull of Hereford, may be mentioned as having paid special attention to the subject. In addition to the mushroom Agaricus campestris and the truffle Tuber æstivum, the following species are wholesome, pleasant to the taste when cooked, easily distinguished from all other species, and more or less abundant in different parts of the country:-Agaricus arvensis, or the horse-mushroom; A. procerus, the parasol-mushroom; A. ostreatus, the vegetable oyster, growing on the trunks of trees; A. melleus, abundant on dead stumps; A. orcella, the vegetable sweet-bread; A. prunulus, the plum-mushroom; Morchella esculenta, the morel; Hydnum repandum, the hedge-hog; Fistulina hepatica, the vegetable beef-steak, on the stumps of hollow trees; Coprinus comatus, very common in gardens; Marasmius oreades, the fairy-ring champignon; Boletus edulis, in woods; and Lycoperdon giganteum, the giant puff-ball, when in the young state, Many of these species are favourite articles of food in the autumn and winter with the peasantry in various parts of the Continent, and are everywhere sold in the markets. Our common mushroom is among the kinds forbidden by the police regulations to be sold in Rome, but is to be met with in the markets of Palermo and Messina. Acclimatization of Half-hardy Plants.-Great efforts have recently been made in France to naturalize trees and shrubs-natives of warmer climates; and these have been attended with considerable success in some instances. The Bamboo, introduced at Tours, Macon, and Angers, has succeeded admirably, and has withstood a very considerable degree of frost. It seems likely to flourish even in the climate of Paris, where it is grown in the gardens of the Société d'Acclimatation. Several species of Eucalyptus, especially the E. globulus, have also been planted extensively in the Department of the Var, where they have been found to resist the destructive northwest wind known as the mistral. The Fertilization of Winter-flowering Plants.-Mr. A. W. Bennett contributes to the first number of the new scientific magazine, 'Nature,' the results of some observations on the fertilization of those plants which habitually flower in the winter, when there are few or no insects to assist in the distribution of the pollen. He finds that in those wild plants which flower and produce seedbearing capsules throughout the year, as the white and red deadnettles, shepherd's purse, chickweed, groundsel, &c., the pollen is uniformly discharged in the bud before the flower opens. Many garden-plants, on the other hand, natives of warmer countries, but which still flower with us in the depth of winter, never bear fruit in this climate, and in them the pollen is not discharged till the flower is fully open. Of this class are the yellow jasmine and the Cheimonanthus fragrans, or all-spice tree; in the latter species the arrangement of the pistil and the stamens is such as to render selffertilization impossible. Leonardo da Vinci as a Botanist.-In the recently commenced 'Nuovo Giornale botanico Italiano,' published at Florence, Signor Uzielli has an interesting article on some botanical observations of Leonardo da Vinci, showing that to the great painter is due the credit of the first observation of certain points in the structure of plants, which has been generally attributed to writers of a considerably later date. The constancy of a uniform arrangement of the leaves on the branches in the same species, known as the Law of Phyllotaxis, is stated in botanical works to have been first observed by Grew and Malpighi towards the close of the seventeenth century. Da Vinci, however, who lived from 1452 to 1519, records observations to the same effect, though not so accurate, in his great Treatise on Painting.' To the same two botanists is also ascribed the discovery of the mode in which the stems of exogenous trees increase beneath the bark by the formation of concentric rings of wood, from the number of which the age of the tree can be determined. This had, however, also been already observed by Da Vinci, and is recorded in passages in the same work. Arctic Flora.-Dr. Berthold Seemann discusses in the Journal of Botany' the question whether vegetation extends to the North Pole, supposing land exists there. He answers the question in the affirmative, maintaining that excessive cold in winter exercises but a limited influence upon a vegetation which, like the Arctic, enjoys the protection of a thick covering of snow, and is besides in a state of inactivity. The temperature of the summer during the months of July and August has by far the greatest share in the distribution. of vegetable life in the northern regions; and the lowest temperature during those months is not found in the most northerly point yet reached by any exploring expedition, but in Winter Island on the eastern shores of the Melville Peninsula, where the mean temperature during July and August ranges between 34° and 36° F. That spot, which may be called the phytological pole, is nevertheless covered with vegetation; and, knowing as we do, that plants do grow not only on a frozen soil, but even, as in Kotzebue Sound, on the tops of icebergs, there is no reason to suppose that the terrestrial pole is destitute of vegetation. The most northerly berry-bearing plant yet recorded is Vaccinium Vitis-Idæa, or the cranberry, gathered in Bushman Island, on the north-west shore of Greenland, by Captain W. Penny, or in latitude 76° N., longitude 66° W. The most northerly berry-bearing genera are Vaccinium, Oxycoccus, Rubus, Cornus, and Empetrum. It is stated that occasionally berries ripen in Lapland. Vegetation of Howe's Island.-The flora of this island, 300 miles from Sydney and 500 from Norfolk Island, has been investigated by Mr. Charles Moore, and is found to resemble much more closely that of the latter island than of Australia. Its situation is 31° 36′ S. lat., 159° 5' E. long.; it is 4 miles in length and 1 in breadth, possesses two mountains about 2500 feet high, and is entirely covered with vegetation, with no barren spots except the coast and the precipitous cliffs. The indigenous species are very few, most of them being peculiar to the island and undescribed. Of Endogens there are four species of Palm, all undescribed and of great value to the natives; two species of Pandanus; three Grasses; two Orchids; a Juncus; a Smilax; one species belonging to Iridaceæ, one to Amaryllidaces, three to Cyperaces, and one to Commelynaces. All the clearings are, however, covered with introduced European plants, including the couch-grass. Among Exogens, the Australian Proteace and Leguminosa are entirely wanting; Epacrida and Myrtacea, so abundant in Australia, are represented, the former by a single species, a tree 30 or 40 feet in height, grow ing at great elevations; the latter by two, the leaves of one of which are used by the natives in the place of tea; a very remarkable undescribed Ficus forms a considerable portion of the larger vegetation, growing sometimes 100 yards across, with very numerous root-stems. The castor-oil plant and Solanum laciniatum are among the most troublesome introduced weeds. Ferns are very abundant, but of non-Australian types; the genera Adiantum and Aspidium, so abundant in Australia, New Zealand, and Norfolk Island, were not observed. The Lichens of Greenland.-Dr. Lauder Lindsay has worked out with great care, in an article read before the Botanical Society of Edinburgh, an account of all that is at present known respecting the Lichens of Greenland. While in 1840 only 59 species had been recorded, Dr. Lindsay is now able to enumerate 268 as natives of Greenland, and thinks that this number may probably be raised to 300. The degrees of latitude within which they have been collected range from 60° to 75°, the majority having come from about 70°, a few from as far north as 82°. The almost entire absence of arboreal vegetation in Greenland necessarily affects the character of the Lichen flora, very few corticole and foliaceous species being found, but a great preponderance of the saxicole forms. One prominent feature is the great abundance of the sombre-coloured Umbilicaria, giving in many parts a funereal colouring to the landscape. Deducting the species that are mainly or entirely confined in their distribution either to Greenland or to Arctic countries, the majority at least of the remainder occur on the Scandinavian Alps, and many of them on the Alps of Scotland and Switzerland, or generally on those of continental Europe; while a considerable number are common British forms. The lichen-flora of Greenland differs, on the other hand, very considerably from that of Arctic America. The lichens of Spitzbergen and its islets are as numerous as those of Greenland, notwithstanding the smaller area; while the whole list of Melville Island lichens contains only twelve species. There is no record of any species of lichen being turned by the Greenlanders to any economic purpose, notwithstanding the abundance of Cladonia rangiferina, or the "Reindeer-moss," and of other species which, in other Arctic countries, have been serviceable in supplying the wants of man or animals. Hibernation of Duck-weed.-It has long been known that some species of Lemna, or duck-weed, produce, at the approach of winter, leaves of a different character to those formed in the spring, which fall to the bottom of the pond or stream, enabling the plant to live through the winter. A series of more accurate observations on this point is recorded by M. Van Horen in the Bulletin de la Société Royale de Botanique de Belgique.' The species of Lemna indigenous to Belgium are the same as those found in this country; of these M. Van Horen finds that two only, the L. polyrrhiza and gibba, produce leaves of a different form in winter; while with the three other species, L. minor, trisulca, and arrhiza, the ordinary leaves live through the winter, remaining on the surface. In L. polyrrhiza these winter-leaves first make their appearance in August or September. They are much smaller than the ordinary leaves, reniform or sometimes elliptical, olive-brown on both sides, and not gibbous beneath; their roots are exceedingly minute, and at first hidden within the leaf. The aëriferous cells which serve to support the ordinary leaves on the surface do not exist, causing the winterleaves to resemble an undeveloped bud. In consequence of the absence of these vessels they are heavier than the water, and fall to the bottom as soon as any agitation of the water detaches them from the parent-leaf, which perishes with the first frost. At the ordinary period of the revival of vegetation, a small bubble of oxygen appears on the upper surface of these submerged leaves, which carries them to the surface, from which they again descend should the temperature fall below a certain point. In Lemna gibba, leaves of a similar character, were observed hibernating beneath the water, differing in shape, size, and structure from those developed during the summer. Evaporation of Water and Decomposition of Carbonic Acid by Plants. An interesting and important series of experiments has been made by M. P. P. Dehérain, of Paris, for the purpose of determining the natural agents most efficacious in promoting the physiological functions of the leaves of plants, the evaporation of water, and the decomposition of carbonic acid. The results arrived at are as follows:-1. These two processes are carried on simultaneously and with corresponding intensity, the same agents which facilitate the one being operative also with the other. They proceed more rapidly from the upper smooth and hard surface of the leaves than from the under-surface. 2. The principal agent in determining these changes is not temperature, but light. While the amount of water given off was hardly affected by any changes of temperature, proceeding almost with equal rapidity even when surrounded by ice; in bright sunshine leaves were found to give off, in long exposure, more than their own weight of water, while in diffused light it amounted to only six to eighteen per cent., and in total darkness was scarcely perceptible. The evaporation and condensation of water proceeded with equal rapidity when the air was perfectly saturated with moisture. 3. The different rays of light are not equally efficacious in promoting these actions. M. Dehérain found, as the result of a number of experiments, that, with an equal intensity of light, the red and yellow rays, which have little photographic power, cause in the same time the decomposition of about five times as much carbonic acid, and the evaporation |