Page:Popular Science Monthly Volume 20.djvu/730

710 Opium-Smoking in America and China. A Study of its Prevalence and Effects, by H. H. Kane, M.D. New York: G. P. Putnam's Sous. 1882. Pp. 156. $1.

Elements of Orthoëpy, consisting of the most Essential Pacts and Principles. By C. W. Larison, M.D. Published by the author at Ringoes, New Jersey. 1881. Pp. 132.

Sewer-Gases: Their Nature and Origin, and how to protect our Dwellings. By Adolfo de Varone, A.M., M.D. Second edition. Revised and enlarged. New York: D. Van Nostrand. 1882. Pp. 145. 50 cents.

Books of All Time. A Guide for the Purchase of Books. Compiled by F. Leypoldt and Lynde E. Jones. New York: F. Leypoldt. 1882. Pp. 80.

A Reading Diary of Modern Fiction. Containing a Representative List of the Novels of the Nineteenth Century, etc. New York: F. Leypoldt. 1881. Pp. 150, with blanks.

The Actual Lateral Pressure of Earth-works. By Benjamin Baker, M. Inst. C. E. New York: D. Van Nostrand. 1882. Pp. 180. 50 cents.

The Mother's Guide in the Management and Feeding of Infants. By John M. Keating, M.D. Philadelphia: Henry C. Lea's Son & Co. 1861. Pp. 118. $1.



Fifty Years' Study of the Distribution of Plants.—Sir J. D. Hooker devoted his address, as President of the Geographical Section of the British Association, to a review of the progress that had been made during the last fifty years in the study of the geographical distribution of living (particularly of vegetable) forms. The germ of this study is to be found in an idea attributed by Humboldt and Forbes to Tournefort, that in ascending mountains the vegetation gradually approaches that of the higher latitudes. Humboldt began his botanical studies early in life, and in his "Prolegomena," published in 1815, endeavored to determine the proportions which the species of certain large families, or groups of families, bear to the whole number of species comprising the floras in advancing from the equator to the poles, and in ascending high mountains. He observed that some kinds of plants increase relatively to others in going from the equator to the poles, others diminish, while some are strongest in the temperate zones, decreasing in both directions. No material advance was made, however, toward improving the laws of geographical distribution so long as it was believed that the continents and oceans had experienced no great changes of surface or climate since the introduction of the existing assemblages of animals and plants. This belief was dispelled by Lyell, who showed, from the examples of Sicily and some of the mountain-regions of Italy, that a fauna may be older than the land it inhabits. Darwin conceived the same idea from comparisons of the living quadrupeds of Asia and America; and it was confirmed by the discovery of Arctic plants on the mountains of the temperate zone. The first attempt to press the result of geological and climatal changes into the service of botanical and zoölogical geography was made by the late Edward Forbes, who communicated to the British Association a study of the distribution of endemic plants, particularly those of the British Islands, considered under this aspect. This paper shows that Forbes was profoundly impressed with the belief that the conditions of geological connection and climate were the all-powerful controllers of the migrations of animals and plants, and induces Professor Hooker to pronounce its author "the reformer of the science of geographical distribution." Before the doctrine of the origin of species by variation and natural selection was published, all reasoning as to the distribution of species was subordinated to the idea that they were permanent and special creations. The modes of dispersion had been traced, but the origin of representative species, genera, and families, remained an enigma. The existence of the same kinds in different places could be accounted for only on the supposition that these different places presented conditions so similar that they favored the creation of similar organisms; and this failed to account for identities occurring where there was no discoverable similarity of physical conditions, and their failing to occur where the conditions were similar. Under the theory of modification of species after migration and isolation, the representation of similar species in distant localities is only a question of time and changed physical conditions. New data for the study of the past and present physical geography of the globe were afforded by the discovery in the Arctic regions of fossil plants of types corresponding with those which are now found only in warm temperate zones, which dates from 1848. These fossils proved not only to belong to genera of trees common to the forests of all the three northern 