Imágenes de páginas
PDF
EPUB

Greenwich records of this star, the following mean annual proper motions in four several intervals:

[blocks in formation]

We may fairly assume that the mean of these values (properly weighted) represents the true value of the star's motion-which it will be seen is exceptionally large.

4. BOTANY.

Evaporation of Water from Plants. Some researches have recently been undertaken by Von Pettenkofer on the amount of evaporation which takes place from the foliage of plants. The experiments were made in the case of an oak tree, and extended over the whole period of its summer growth. He found the amount of evaporation to increase gradually from May to July, and then decrease till October. The number of leaves on the tree were estimated at 751,592, and the total amount of evaporation in the year at 539 16 cubic centimètres of water for the whole area of the leaves. average amount of rainfall for the same period is only 65 cubic centimètres; the amount of evaporation is thus 8 times more than that of the rainfall. The excess must be drawn up by the roots from a great depth; and thus trees prevent the gradual drying of a climate, by restoring to the air the moisture which would otherwise be carried off by drainage.

The

Germination of Palms.—Mr. J. W. Jackson, Curator of the Museum at Kew, has published a useful paper "On the Germination of Palms." This is incorrectly described in all the botanical text-books commonly in use. The peculiarity consists in the end of the cotyledon remaining in the seed, whilst its stalk is pushed out, carrying with it the radicle, which germinates in the usual manner at a little distance from the seed. In the double cocoa-nut, Lodoicea, the protruded end of the cotyledon is as much as 12 or 18 inches long. The sheath or socket at the base of the stem of this palm is shown not to be peculiar to it, as has been supposed, though more developed than in other species, and to be formed by the vascular bundles of the rudimentary and early leaves.

Existence of a Formative Layer in the Leaves of Plants.— M. Cave has recently pointed out that a formative layer exists in the leaves of plants, similar to the well-known cambium layer, which, in exogenous plants, intervenes between the bark and the

wood, and from which the new wood is formed. He finds it not only in the leaves, but in all foliar or "appendicular" organs, normal or modified, as for instance the flowers, but occupying a different position to the cambium layer, namely, between the tissue of the organ itself and the epidermis. The knowledge of this fact M. Cave applies to determine a morphological question which is often a matter of controversy, whether a particular organ belongs to the axis, to the foliage, or to both sets of organs combined; and he shows that if the formative layer is exterior to the fibro-vascular system, the organ belongs to the leaves; if interior to it, to the stem. The application of this test proves that the receptacle-like perigynous calyx of many plants is a dependency of the axis; while the pericarp of superior fruits is always formed of metamorphosed leaves and nothing else; this is also the case with the axile and parietal placentæ; but the free central placenta, as in the case of Primulaceæ, is a prolongation of the axis. Fruits proceeding from an inferior ovary are composed of two parts, varying in their mutual proportion in different plants, a receptacle-like calyx and carpellary leaves. It is noteworthy that M. Cave found this formative layer to occupy the same position in the leaves and fruits of endogens as in those of exogens.

Changes in the Colour of Flowers produced by Ammonia.— M. Vogel has recently published the results of some experiments on the changes produced by ammonia in some vegetable colours, especially those of flowers, which he thinks may be of practical importance in the manufacture of vegetable colouring matters of a character similar to the aniline dyes. The colouring matter he states to be of two kinds, united with a different degree of persistence to the tissue of the flower itself, and requiring a shorter or longer time to produce any alteration. The change produced in the colour of some flowers, as the rose and phlox, by the fumes of tobacco, is entirely due to its ammoniacal element. M. Vogel found that some colours are altogether unchanged by lengthened exposure to ammonia; as, for instance, yellows, all reds (except in the case of the Zinnia, which is converted into a brown-red), and dark violets. Blue is sometimes unaltered, sometimes changed into a dirty green and then bleached. In some cases, not only the colour but the tissue of the flower is destroyed. The changes are generally the same as those that take place during the withering of the flower.

Electricity in Plant Life.-A writer in the Gardener's Chronicle' points out the important part played by electricity in the phenomena of vegetable life. He states that every hair and sharp point in the vegetable kingdom is necessarily a conductor of electricity, which must always be present wherever water rises in the form of vapour. Hence all the young and growing parts of

plants are clothed with delicate hairs; and the same is generally the case with those fruits or other parts which have a very fine and delicate scent or flavour, these qualities being, the writer believes, greatly developed by the agency of electricity.

Poisoning by Enanthe crocata.-Mr. Worthington G. Smith records an instance of poisoning by the water dropwort, Enanthe crocata, a common Umbelliferous plant in the South of England. A carter, whilst at work, ate some of the roots, supposing them to be wild parsnips; in about an hour he became unconscious and convulsed, and death occurred in another half-hour, before medical assistance could be obtained. The man had fed his horse with roots of the same plant, and the animal also expired about two hours after eating them. The plant belongs to that group of narcoticoacrid poisons comprising the Solanaceae (Belladonna, Hyoscyamus, &c.), and characterized by producing convulsions with delirium. The juice of the plant was in this instance of a yellow colour; it has been stated that a variety of the plant with colourless juice is a less virulent poison. The taste of the root is said to be intermediate between that of celery and turnip.

Mistletoe on the Oak.-Dr. Bull records, in the 'Transactions of the Woolhope Naturalists' Field Club,' a very interesting case of this extremely rare occurrence. The tree grows in the hedge-row of a field called the Harps, at Haven Aymestry, in the ancient forest of Deerfold, in Herefordshire. It was discovered in the spring of 1869, but the mistletoe must have been growing on the oak for some years. The oak is of the variety sessiliflora, and may be some fifty or sixty years old. The mistletoe is a female plant, and grows high up on the main stem. It forms a large spreading bunch, with a diameter of 3 feet 6 inches, and springs out from the oak in a single stem, nearly 4 inches in circumference. The mistletoe is also growing on a thorn close by, and has probably sprung from a seed dropped by a bird from above. The great rarity of the growth of mistletoe on the oak is proved by the fact that there are but eight examples which have been well authenticated as existing at the present time; the localities being Eastnor Park, Herefordshire; Tedstone Delamere, Herefordshire; Forest of Deerfold, Herefordshire; Frampton-on-Severn, Gloucestershire; Sudbury Park, Monmouthshire; Dunsfold, Surrey; Hackwood Park, Hants; and one near Plymouth.

The Cinchona in the West Indies.-In a recently-issued Colonial Blue-Book, Sir James P. Grant, the Governor of Jamaica, states that the cinchona plantation in that island may now be pronounced a complete success. Cinchona plants were first received in 1866. By the close of 1867 the number of young plants had so much increased, that it became necessary to provide land for their final establishment on a planter's scale. Six hundred acres of

virgin forest in the Blue Mountain were acquired early in the year, and were set apart for the purpose of a cinchona plantation, for which the place is in every way admirably suited. The elevation varies from 4000 to 6000 feet. It is well watered, has the best aspects, and possesses a soil reported to be admirably adapted to the requirements of the cinchona. Fifty acres were cleared, of which forty were filled with cinchonas in the course of the year; about 20,000 plants of five different species having been planted. By the latest accounts all of these were in full vigour, and the plantation must by this time be doubled in extent. The plants have stood one of the driest seasons that has ever been remembered on Blue Mountain, without suffering in the least. There is now no doubt that the cinchona can be successfully reared in Jamaica.

Origin of Prairie Vegetation.-Professor Winchell, of the University of Michigan, has recently promulgated a new theory respecting the origin of the vegetation of the American prairies, namely, that it dates back beyond the historical epoch to the Glacial period. He believes the origin of the prairies to be lacustrine; but, contrary to the generally-received opinion, he maintains that lacustrine sediments contain no living germs. Diluvial deposits, he states, on the contrary, are found everywhere replete with living germs, which, when hidden away from the influence of light and moisture, retain their vitality or power of germination for an indefinite length of time. These living germs of the diluvial deposits he believes to have been buried during the glacial period, in the course of which the surface was ploughed up by glaciers, and afterwards exposed to the commotion of the sea, which overspread the land, burying everything in promiscuous ruin; but yet by this very means storing away the seeds which, when brought to the surface after the lapse of a geological age, are possessed of vitality, and able to reclothe the barren earth with verdure and beauty. Thus, in proportion as the diluvial surface became exposed, the flora of the pre-glacial epoch was reproduced. In support of this theory, he brings forward the argument that the fossil plants which have been discovered in the tertiary deposits show a correspondence of genera, and in some cases even of species, with those existing at the present time.

The Herbarium of the British Museum.-The Curator of the British Museum Herbarium has just published his annual report of the national collection. A considerable number of families have been re-arranged, and collections incorporated in the general herbarium from Mexico, New Granada, Nicaragua, Ecuador, California, India, and other countries. The most important additions to the herbarium have been 2000 plants from Abyssinia, and upwards of 3000 from South Africa, as well as more than 1000 European plants, and a number of smaller collections. Various portions of

the British herbarium, and the collection of fruit and seeds, have been re-arranged, and the recent and fossil Coniferæ and Cycadeæ have been examined and arranged.

The Botanic Garden at Brussels.-The Belgian Government recently purchased the magnificent collection of dried plants of the late Von Martius as the nucleus of a national herbarium. It has more recently concluded the purchase of the Botanic Garden belonging to the Horticultural Society of Belgium; and has thus commenced the formation of a national establishment intended to rival those of Paris and London.

5. CHEMISTRY.

Or all the non-metallic elements, fluorine appears the most difficult to bring under the domain of organic chemistry; very few compounds of this element with carbon, hydrogen, and nitrogen being known. Dr. R. Schmitt and H. von Gehren have recently succeeded in preparing Fluorbenzoic acid and Fluorbenzol. Fluorbenzoic acid is prepared from diazo-amidobenzoic acid by treating that substance at a high temperature in a platinum basin with hydrofluoric acid. The fluorbenzoic acid thus obtained resembles, as far as its physical properties are concerned, benzoic acid; it is, however, far more volatile, fuses at 182° C., is difficultly soluble in cold, readily in hot water, and soluble also in ether and alcohol; its aqueous solution exhibits a strongly acid reaction to test-paper and decomposes inorganic carbonates very readily; the acid does not act upon glass, and is a very fixed substance, which may be even dissolved in concentrated sulphuric acid without decomposition. Fluorbenzol is a crystalline solid, boiling at about 183° C., fusing at 40°, insoluble in water, and specifically heavier than that liquid, readily soluble in ether and alcohol.

Whilst organic chemistry is aptly called the chemistry of carbon, Drs. Friedel and Ladenburg are engaged in researches which tend to place silicium parallel to the former element. They have succeeded in preparing what they call silico-propionic acid, a compound wherein a large percentage of the carbon of propionic acid is replaced by silicium. The physical aspect and many of the properties of this body are akin to silica; but it is a combustible substance, insoluble in water, but soluble in a hot and concentrated solution of caustic potassa. M. Dumas observed, in reference to this paper, that it is not impossible that there exist in nature organic compounds of silica, a remark which gave rise to some observations on Dr. Friedel's Memoir,' by P. Thenard. The author begins with stating that M. Dumas is quite right, and

« AnteriorContinuar »