Page:Popular Science Monthly Volume 4.djvu/396

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382
THE POPULAR SCIENCE MONTHLY.

in France, but hitherto without success. The latest remedy, one from which great results were expected, is sulphuret of carbon. It was held that this substance is fatal to the phylloxera, but perfectly harmless to the vines. As to the first point, there appears to be no reason to question the beneficial effects of the sulphuret, but not so with regard to the second, if we may put any faith in the experiments of Lecoq de Boisbaudrant. According to him, sulphuret of carbon kills the vine as well as its parasite.

 

Migrations of Insects.—The following historical facts will give an idea of the enormous magnitude sometimes attained by migrating swarms of insects. After the defeat of Poltava, while retreating through Bessarabia, Charles XII.'s army was marching through a defile, when suddenly the men and horses were brought to a halt, being blinded by a living hail precipitated from a thick cloud which intercepted the light of the sun. The coming of the locusts was heralded by a whizzing sound like that which precedes a storm of wind, and the noise of their wings and of their bodies as they clashed together was greater than the roar of breakers on the sea-shore! General Levaillant saw, at Philippeville, Algeria, a cloud of locusts twenty to twenty-five miles in length, which, when it descended to the earth, formed a layer over an inch in thickness.

Toward the close of 1864 the cotton plantations of Senegal were destroyed, and a living cloud was seen to pass over the country from morning till night: the rate at which it moved showed that it was about fifty miles long; and this was only the vanguard, for when the sun went down a still denser cloud was moving on. The English traveller, Barrow, states that in Southern Africa, in the year 1797, these insects covered the ground to the extent of two square miles, and that having been driven by the wind toward the sea, they formed a drift near the coast nearly four feet in depth and fifty miles long! After the wind changed, the stench of their putrefying carcasses was recognized at the distance of a hundred and fifty miles.

The famines produced by the voracity of these acridians are not the only evils they cause to men and animals; a pestilential epidemic is oftentimes the result of the foul emanations from their rotting bodies. The invasions of these insects are veritable national calamities. In 1835 China was ravaged by them, and the sun and moon were obscured. Wherever they alighted the finest and richest crops were instantly devoured and the fields left bare; even the contents of the barns were to a great extent consumed by them. The people fled in alarm to the mountains. In the submerged districts, where there were no crops to devour, the locusts penetrated into the houses and destroyed the people's clothing. These ravages, which began in April, continued without interruption till the season of frost and snow.

 

Animal-like Functions of Plants.—In the Biological Section of the late meeting of the British Association, Dr. Burdon Sanderson read a paper on the electrical phenomena which accompany the contractions of the leaf of Venus's-Flytrap. It was remarked that in those structures in the higher animals which are endowed with the property of contracting when stimulated, viz., nerve and muscle, this property is associated with the existence of voltaic currents which have definite directions in the tissue. It became suspected that such was similarly true of the Sundew (Drosera), and Venus's-Flytrap (Dionæa muscipula) and some other plants. Mr. Darwin furnished the plants necessary for experiment to Dr. Sanderson in the laboratory of University College, London. The result is, that the anticipations of the existence of voltaic currents in these parts have been confirmed, particularly in the leaf of Dionæa. The doctor has established the fact that these currents are subject, in all respects in which they have been investigated, to the same laws as those of muscle and nerve. This may be regarded as one of the most interesting of recent biological discoveries.

 

Natural Varieties.—Nature's best efforts in the vegetable kingdom sometimes seem to be reached per saltum, and without any aid from man. Recently in England a first-class certificate was given by the Royal Horticultural Society for a fine variety of gooseberry,