136 



POPULAR SCIENCE MONTHLY. 



whole ; Prof. E. B. Poulton, in the Section 

 of Zoology, discussed the difficulties which 

 arise from both the physical and the bio- 

 logical points of view in considering the 

 subject of organic evolution, and inquired 

 whether the present state of paleontological 

 and zoological knowledge increases or di- 

 minishes those difficulties ; Major Leonard 

 Darwin, of the Royal Geogiaphical 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 trav- 

 erse ; 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 accom- 

 plished in the several departments of civil 

 and mechanical engineering during the quar- 

 ter of a century since the association last met 

 in Liverpool ; Mr. Arthur J. Evans, in the 

 Section of Anthropology, dealt with the Ori- 

 gins of Mediterranean and European Civili- 

 zation, 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 Modem Morphological Botany. 



The Tree-Emblem of the Sioux. la a 



paper on The Emblematic Use of the Tree in 

 the Dacotan Group, read as a vice-presiden- 

 tial address before the Anthropological Sec- 

 tion of the American Association, Miss Alice 

 C. Fletcher, after showing how the religions 

 of the Indians probably began with the ut- 

 terances of a seer, which, passing from mouth 

 to mouth, gradually developed into cere- 

 monials with their rites, spoke of the thun- 

 der as the universally accepted manifestation 

 of Wa-kanda, the mysterious power perme- 

 ating 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 Da- 

 cotans. 



Baiafall and the Forms of Leaves. Ob- 

 servations 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 ac- 

 tion 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 pre- 

 sents new points of view and contains very 

 instructive details. The morphological pe- 

 culiarities described are explained by Stahl 

 as results of the necessity of relieving the 

 leaves from their load of moisture, of turn- 

 ing the water to the roots and freeing the 

 tops of the plants from it, of freeing the 

 leaves from epiphytic alga?, fungi, and li- 

 chens, 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 trop 

 ical 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 Ger- 

 man TrdufehpUze7i, 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 green- 

 houses, to modify the shape of leaves by ex- 

 posing 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 



