Page:Popular Science Monthly Volume 50.djvu/148

136 whole; Prof. E. B. Poulton, in the Section of Zoölogy, discussed the difficulties which arise from both the physical and the biological points of view in considering the subject of organic evolution, and inquired whether the present state of paleontological and zoölogical knowledge increases or diminishes those difficulties; Major Leonard Darwin, of the Royal Geographical Society, described what has been done for railway construction in Africa and what remains to be done if the continent is to be opened up, and sought to indicate the relation of the proposed railway routes to the main physical features of the countries they are to traverse; Mr. Leonard Courtney, M. P., in the Section of Economic Science and Statistics, presented a qualified defense of individualism as opposed to the principles of collectivism; Sir Douglas rox,in the Section of Mechanics, sketched the progress that had been accomplished in the several departments of civil and mechanical engineering during the quarter of a century since the association last met in Liverpool; Mr. Arthur J. Evans, in the Section of Anthropology, dealt with the Origins of Mediterranean and European Civilization, supporting the "Eurafrican" theory in contradistinction to the Aryan theory; Dr. G. H. Scott, in the Botanical Section, presented an Exposition of the Scope and Functions of Modern Morphological Botany.

The Tree-Emblem of the Sioux.—In a paper on The Emblematic Use of the Tree in the Dacotan Group, read as a vice-presidential address before the Anthropological Section of the American Association, Miss Alice C. Fletcher, after showing how the religions of the Indians probably began with the utterances of a seer, which, passing from mouth to mouth, gradually developed into ceremonials with their rites, spoke of the thunder as the universally accepted manifestation of Wa-kan-da, the mysterious power permeating life. This idea was connected with the thunder birds, and they lived in cedar trees. The pole of the cedar tree therefore became an emblem of the highest value, so that the ceremonies of the sacred pole were of the greatest importance. The development of this idea slowly through many years is a most interesting part of the story of the Dacotans.

Rainfall and the Forms of Leaves.—Observations made by Stahl at Buitenzorg, Java, and recorded in his book on Rainfall and the Forms of Leaves, establish the fact that the points and indentations of leaves are elongated and made more slender by the action of rain; that leaves under its influence tend to assume a vertical position; that the nerves are modified into little channels through which water can flow easily; and that the arrangement of the down on leaves and stems contributes to the scattering of the drops. Other observers, Lundstrom and Wille, for example, had already pointed out some of these facts, but Stahl's work presents new points of view and contains very instructive details. The morphological peculiarities described are explained by Stahl as results of the necessity of relieving the leaves from their load of moisture, of turning the water to the roots and freeing the tops of the plants from it, of freeing the leaves from epiphytic algæ, fungi, and lichens, and of drying their surfaces rapidly, thereby making transpiration more easy. The distinctive feature of leaves exposed to seasons of rain is the elongation of their points, and this form appertains not to tropical plants only, but also to those which grow on the beach and receive the spray from the sea, to plants on high mountains and elevated plateaus which are wet by heavy dews, and to plants of the temperate zones growing where the precipitation is considerable. New and interesting observations on this subject are contained in a work recently published by Jungner. Some of the most original of them relate to the influence exercised by the spray of waterfalls on the plants that grow in the gorges, below or by the side of the falls. Plants situated thus are styled in German Träufelspitzen, or drip-pointed. In the leaves exposed to the spray, their usual down, which would tend to retain the moisture for some time, disappears from the leaves; and the grouping of the leaves on the stems is observed to be favorable to the passing away of the water. These effects may be produced experimentally; and it is possible, in greenhouses, to modify the shape of leaves by exposing them constantly to a fall of water or to spray. Jungner's experiments all tend to the support of the modern ideas concerning adaptation. These conclusions were reviewed