THE POPULAR SCIENCE MONTHLY.
capable of growth, by bending in different directions—phenomena familiar to vegetable physiologists. But two years ago other phenomena were observed, which did not appear to belong to any of the known categories. Elfving found that pieces of iron and, to a less-degree, of zinc or aluminium, as well as different organic substances, such as sealing-wax, rosin, etc., attracted the growing sporangium-bearing filaments of a mold (Phycomyces nitens). All other metals Elfving found inactive, but the filaments of the mold itself showed a mutual repulsion. This movement, however, Prof. Errera considered wholly due to the hygroscopic condition of the stimulatory substance. The sensibility of phycomyces, he observed, was in fact so great that it might be used as a reagent to test the existence of hydroscopic power, which he illustrated in the case of camphor, the hydroscopic condition of which, after one experiment, was proved by careful weighing, although it was unknown to chemists. All the experiments succeeded in a saturated atmosphere, showing that hydrotropism was not due, as generally believed, to difference in the hygrometric state of the air. To sum up, concluded the author, the apparently mysterious action of iron on phycomyces was nothing but a matter of hydrotropism, and hydrotropism itself, negative or positive, was the bending of a vegetable organ toward the points, not where it would find a minimum or maximum of moisture, but where it would transpire most or least.
Disappearance of Wild Plants.—The report of the committee of the British Association on the disappearance of wild plants from their native habitats mentioned fifty of the less common wild plants of the west of Scotland which had been greatly reduced in number in recent years from natural and other causes. The natural causes were due to agriculture, drainage, industry, and the growth of towns and villages, and seemed to be outside of the scope of protective measures. In many cases disappearance is attributable to the removal of specimens by collectors for the formation of herbariums, and of plants with showy flowers and ferns for sale. Herbariums are essential to the study of botany, but the committee thought their multiplication might be made unnecessary by the formation of local collections for reference. Collections for sale might be prevented by the intervention of proprietors. But it was difficult to suggest any course of prohibitive measures. In the discussion the too specific designation of places where choice plants can be found was deprecated as making access to them too easy to unscrupulous searchers. A resolution was passed on the preservation of birds and eggs; and Canon Tristram, speaking to it, put in a plea for the preservation of birds of prey, pointing to the mice-plague in Dumfries and Lanark shires as a result of destroying the balance of Nature by wholesale killing of such birds.
Prize Essays on Alcohol.—The American Medical Temperance Association, through the kindness of J. H. Kellogg, M. D., of Battle Creek, Mich., offers the following prizes:
1. One hundred dollars for the best essay On the Physical Action of Alcohol, based on Original Research and Experiment.
2. One hundred dollars for the best essay On the Non-Alcoholic Treatment of Disease.
These essays must be sent to the secretary of the committee, Dr. Crothers, Hartford, Conn., on or before May 1, 1893. They should be in type-writing, with the author's name in a sealed envelope, with motto to distinguish it. The report of the committee will be announced at the annual meeting at Milwaukee, Wis., in June, 1893, and the successful essays read. These essays will be the property of the Association, and will be published at the discretion of the committee. All essays are to be scientific, and without restrictions as to length, and limited to physicians of this country. Address all inquiries to T. D. Crothers, M. D., secretary of committee, Hartford, Conn.
Devolution of the Little Toe.—The thumb and great toe of men are two-jointed, while the other fingers and toes are three-jointed. But it has been observed, in the examinations of skeletons, that the little toe is occasionally two-jointed; the middle and terminal phalanges having been so united that they can hardly be distinguished. This variation occurs in about thirty-six per cent