rise in Tibet from lakes full of fish, but have none (at least during the rains) in that rapid part of their course from 10,000 to 14,000 feet elevation; below that fish abound, but invariably of different species from those found at the sources of the same rivers. The nature of the tropical ocean into which all the Himalayan rivers débouche, is no doubt the proximate cause of the absence of Salmonidæ.—Hocker's Himalayan Journal.
BOTANY.
Sheep Sorrel in New Zealand.—One of the greatest pest of this country (on the cultivated lands) is the common English Sheep-sorrel (Rumex acetosella), called by the natives the red sorrel, and said by them to be a native of Tasmania. This plant spreads with singular rapidity, its roots forming a perfect mat, and the smallest fragment throwing up a stem. Where it is present in the ground scarcely any of the ordinary crops can be obtained. All the usual processes of cultivation, such as fallows, &c., utterly fail even to mitigate the evil, and farmers were in despair, until it was found, that in the "struggle for existence," even this weed could not make head against the greater vigour of the white clover. I have seen hundreds of acres of broken-up land so completely overgrown with this plant, as to appear like a uniform red patch in the landscape, but upon which, at the end of two years, after it had been "laid down" with white clover and Italian rye-grass (which by itself would have done no good), scarcely a specimen of the sorrel could be found.—Travers, in Natural History Review.
Most Perfect Plants.—Those plants are most perfect, in which the organs discharging different functions are most distinct both in position and structure. The thalloid fronds (of Cactaceæ) and the hypoblastoid embryos of Endogens indicate a lower degree of organization. Plants which have the stamens and pistils either naked or in the axil of an unmodified leaf (Naias, Hippuris, Callitriche) are inferior to those whose flowers are never complicated. Diclinous flowers are lower in position than those which are hermaphrodite; ternary verticils lower than quiniary, spirally arranged floral organs lower than those which are verticillate, polypetalous flowers lower than synearpous, atropous ovules lower than those which are inverted, homogenous embryos lower than those which are fully developed. Trees and shrubs are more common among imperfect plants. In the lower orders flowers are very numerous, in the higher the number of seeds produced by each flower is very great. Yellow and green colours in the flowers of the lowest rank are changed into red or white in those of a higher order, and in the highest plants the colour of the flower is generally blue.—J. G. Agardh. Theoria Systematis Plantarum.
A Horse-chestnut Tree.—Dr. Davy read a paper at Bath on the horse-chestnut; will any one read a paper of a horse-chestnut? The tree stands on a flat stone. Its root grows up through the air for 7 feet, turns over a wall, and descends 7 feet into the earth. So that the root passes for 14 feet through the air before it enters the earth. The celebrated Dutrochet, by experiment, convinced the still more celebrated De Candolle, and all European vegetable physiologists, that roots will only grow straight downwards. On this, I set to work to show that they will grow in any direction in which they can find food. If any one doubts this fact, let him inspect my tree, which is now twenty-one years old. In imitation of Dutrochet's beautiful experiment, I placed a great variety of seeds (single as well as double) in flower-pots, suspended them upside down on wire-work, and watered them from above. Each seed sent a tap-root down into the air, which died; but the branch roots (as I have named them) and the plants grew, and corn ripened in this way. But cuttings placed upside down, though they grew and bore fruit for years, showed no root below. I thus blundered on the fact that every seedling has a top-root, whose downward determination nothing can pervert, a provision and contrivance for the fixing of the plant, and a beautiful proof of the design of a Creator. But the downward tap-root is as peculiar to the seedling as the "seed-leaves" are, and all branch roots will grow in all directions. I preserved one horse-chestnut by placing it on a flat stone, and replacing the flower-pot with a chimney-pot full of earth, and, by degrees, raised a column of chimney-pots. I then built up a column of earth on the opposite side of the wall, turned the roots into it, and when they were established in the ground, I took away the two columns of earth. I think that Virgil's tap-rooted Esculus is the horse-chestnut. Virgil mentions it as distinct from the quercus and castanea, and Ovidas distinct from the fagus and ilex. It is, then, a feat to make its radix tend to heaven instead of to Tartarus. With regard to the name from Esea, it is true that neither man, horses, nor pigs will eat horse-chestnuts, but sheep, cows, and deer are ravenously eager for them.—Col. Greenwood, in Athenæum.
Plants Rooting in the Soil.—Plants themselves send down their roots naturally to a depth which, strange to say, is so little known as scarcely to be credited. In the case of beans, turnips, and red clover, we are familiar with the fact, that their