Page:Popular Science Monthly Volume 5.djvu/135

Rh The Potato-Disease.—It is quite certain that the same stock grown on the same land, for several years in succession, deteriorates considerably; and, as the vigor of the plant declines, it becomes more and more susceptible to toe influence of unfavorable weather. It will generally be found, says the Gardeners' Magazine, that in a year of disease the sorts regarded by the cultivator with interest as novelties, turn out the best; while those that have been grown on the same spot for several years, suffer most severely. The novelties usually come from a distance, and, irrespective of their intrinsic merits as varieties, they have this peculiar advantage, that they were raised on a different soil, and to some slight extent in a different climate from that they are used to depend on for subsistence.

Generally speaking, says the same magazine, the best seed for strong soils is that raised on peat and bog lands, and seed of excellent quality may be obtained from dry, calcareous soils and newly-broken, sandy pastures. It is very much the custom in England for traders who have to provide largely of seed-potatoes for their customers, to send certain sorts to growers occupying such lands, in order to secure vigorous stocks for cultivation the next year on strong, productive lauds. The seed so obtained produces a cleaner crop in a bad season, and a heavier crop in a good season, than seed of the same sorts that has not enjoyed a change of soil for many years. Hence, purchased seed is, as a rule, better than that of the same sort home-grown.

Microscopic Aspects of the Potato-Disease.—Mr. Wenham, writing in the Microscopical Journal on the subject of potato-blight, says that a fungus, from the universal presence of the spores in damp localities, and its rapid growth, may appear simultaneously with morbid conditions, and yet not be the primary cause. The grape-vine disease, being cuticular, may be readily traced by the microscope to a fungoid origin, and this origin is further proved by the action of the sulphur-cure, so destructive to fungi in confined localities. This is of no avail in the potato-disease, which, under conditions favorable to its development, is internal and constitutional.

On placing a very thin slice of potato (taken at any time of the year) under the microscope, the cells are seen to be filled with starch-granules, and the walls coated with a layer of active protoplasm of the usual molecular appearance. In the healthy cell, this protoplasm, when seen under the highest powers, with suitable illumination, has a vibratory motion, with feeble currents, in various directions. On approaching the vicinity of the diseased portion, the cell-walls begin to appear of a light-brown color, and wherever the least tinge of this becomes apparent there is no movement, nor can any protoplasm be detected adhering to the wall of the cell, which from that time is a dead member.

Tracing the cell-walls farther, the color deepens, and the septa become thicker, till at last the walls split, giving the now rotten cell a detached appearance; but, from the first indication of disease to the final rotten state, no vital activity can be discovered. In all the phases the starch-granules remain unaltered, completely resisting this peculiar decomposition. The disease is evidently located throughout the tuber, in the substance of the cell-walls. Of its origin Mr. Wenham offers no opinion.

English Honors to an American Astronomer.—The British Royal Astronomical Society has awarded a gold medal to Prof. Simon Newcomb, Astronomer-in-Chief of the United States Observatory at Washington, for his Tables of Neptune and Uranus, and for other valuable astronomical work. The "Investigation of the Orbit of Uranus, with General Tables of its Motion," is the result of fifteen years of labor under the immediate supervision of Prof. Newcomb. Prof. Cayley, of the Astronomical Society, in presenting the medal to Dr. Huggins for transmission to Prof. Newcomb, spoke in very high terms of commendation of the Washington astronomer, and concluded as follows: "Prof. Newcomb's writings exhibit, all of them, a combination, on the one hand, of mathematical skill and power; and, on the other hand, of good, hard work, devoted to the furtherance of astronomical science. The memoir on the lunar theory contains the successful development of a highly-original idea, and cannot but be regarded