516 



SCIENCE 



[N. S. Vol. XLVI. No. 1195 



parative study of myths current among Amer- 

 ican Indians and in the interpretation of them. 

 John E. Swanton 

 Smithsonian Institution, 

 "Washington, D. C. 



The Genus Plioradendron. By William 

 Trelease, Professor of Botany in the Uni- 

 versity of Illinois. Published by the Uui- 

 versity. Octavo, pp. 224, pis. 245. Price, 

 paper, $2.00; cloth, $2.50. 

 It is fortunate for botanists that the author 

 of this excellent treatise has made so thorough 

 a revision of the genus Plioradendron instead 

 of being content with merely attempting to 

 straighten out the tangle existing in regard 

 to the group of related forms hitherto known 

 as Phoradendron flavescens, as he first con- 

 templated. The author notes that Engelmann 

 has shown too great a conservatism in his 

 published studies of the various forms of 

 species of the genus, by later withdrawing 

 segregates of P. flavescens that he formerly had 

 recognized, and that in continuing the work 

 of Engelmann, also being influenced by his 

 views, Torrey allowed a number of forms which 

 he had designated as new species to lie unpub- 

 lished in the Torrey herbarium. The author 

 in addition to making a critical study of the 

 abundant data and material of Iforth Ameri- 

 can species collected by Engelmann, Torrey 

 and others in the great herbaria of this 

 country, visited those of Europe and extended 

 the investigation to the collection of West 

 Indian and South American species by 

 Urban, Martins and others. This has en- 

 abled him to make a careful comparison of 

 numerous types and variants of species of the 

 genus, and to more carefully discriminate be- 

 tween varieties and species. He recognizes 

 262 differentiable forms, most of which he 

 has classified as species. In this matter he 

 apparently does not share the conservatism of 

 Engelmann and Torrey. Of the species he 

 now recognizes, 154 are listed from North 

 America and 124 from South Am erica. The 

 genus is separated into two primary groups, 

 the Boreales and the ^quatoriales, plants of 

 the former are constantly without, and the 

 latter constantly with cataphyls on their foli- 



age shoots. Both groups contain species 

 destitute of expanded foliage, which are well 

 represented by Phoradendron juniperinum in 

 the southwestern United States. All of our 

 species "belong to the Boreales, those of Mexico 

 and Central America to both primary groups, 

 and those of the West Indies and South 

 America wholly to the ^quatoriales. These 

 primary groups are each divided and then 

 subdivided, making finally in all groups 55 

 minor subdivisions. 



The book contains 224 pages of descriptive 

 matter including very good and usable keys; 

 these are supplemented by indexes of col- 

 lectors, occurrence, and names. The illustra- 

 tions, 245 full sized plates, are indeed works 

 of art but are also true to nature. Few books 

 of this class are so fully and beautifully 

 illustrated. George G. Hedgcock 



MECHANICAL PROPERTIES OF WOOD 

 DETERMINED 



A NUMBER of fundamental laws governing 

 the properties of wood, such as those covering 

 the relations between strength and specific 

 gravity, and between strength and moisture 

 content, are laid down in a bulletin just issued 

 by the Department of Agriculture. In this 

 publication are presented the results of about 

 130,000 strength tests, probably the largest 

 single series ever run on one material, made 

 by the Forest Products Laboratory of the 

 Forest Service on 126 species of American 

 woods. The laws derived from the tests cover 

 the general relations existing between .me- 

 chanical and physical properties of each 

 species, and also the general relations existing 

 between these properties irrespective of 

 species. 



The results ought to prove of great value 

 wherever knowledge of the properties of wood 

 is essential. They have, for example, made 

 possible the preparation of accurate tables 

 showing all the needed strength properties for 

 the woods used in airplanes. With these as a 

 basis, specifications can be drawn up to elimi- 

 nate all material that does not meet the exact- 

 ing requirements of this highly specialized 



