112 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1921. 



No. 5. New selaginellas from the western United States. By William R. 



Maxon. December 22, 1920. 10 pp., G pis. (Publ. 2589.) 

 No. 6. Explorations and field-work of the Smithsonian Institution in 1920. 



May 12, 1921. 120 pp., 13S figs. (Publ. 2619. 1 

 No. 7. Sea-lilies and feather stars. By Austin II. Clark. April 28, 1921. 43 



pp., 16 pis. (Publ. 2620.) 

 No. 9. Neoabbottia, a new cactus genus from Hispaniola. By N. L. Britton and 



.T.N.Rose. June 15, 1921. 6 pp., 4 pis. (Publ. 2051.) 



SMITHSONIAN ANNUAL REPORTS. 



REPORT FOR 10 IS. 



The complete volume of the Annual Report of the Board of 



Regents for 1918, together with pamphlet copies of the papers in the 



general appendix, was received from the Public Printer during the 



year. 



Annual Report of the Board of Regents of the Smithsouian Institution, show- 

 ing operations, expenditures, and condition of the Institution for the year 

 ending June 30, 1918. xii 4- 012 pp., 54 pis., 128 text figs. (Publ. 2549.) 



The appendix contained the following papers : 



The Discovery of Helium, and What Came of It, by C. G. Abbot. 5 pp. 



(Publ. 2550.) 

 An Account of the Rise of Navigation, by R. H. Curtiss. 11 pp. (Publ. 2551.) 

 The Tornadoes of the United States, by Prof. Robert DeC. Ward. 6 pp., 1 pi. 



(Publ. 2552.) 

 Wind Power, by James Carlill. 9 pp. (Publ. 2553.) 

 A Tribute. Samuel Pierpont Langley : Pioneer in Practical Aviation, by 



Henry Leffman. 10 pp., 9 pis. (Publ. 2554.) 

 Twentieth Century Physics, by. R. A. Millikan. 19 pp. (Publ; 2555.) 

 The Experiments of Dr. P. W. Bridgman on the Properties of Matter When 



Under High Pressure. Introductory Note by C. G. Abbot. 19 pp., 1 pi. 



(Publ. 2550.) 

 The Problem of Radioactive Lead, by Theodore W. Richards. 14 pp. (Publ. 



2557. ) 

 Sphagnum Moss : War Substitute for Cotton in Absorbent Surgical Dressings, 



by Prof. George E. Nichols. 13 pp., 4 pis. (Publ. 2558.) 

 History of Military Medicine and its Contributions to Science, by Col. W. P. 



Chamberlain. 14 pp. (Publ. 2559.) 

 Some Problems of International Readjustment of Mineral Supplies as Indicated 



In Recent Foreign Literature, by Eleanora F. Bliss. IS pp. (Publ. 2500.) 

 Reptile Reconstructions in the United States National Museum, by Charles W. 



Gilmore. 10 pp., 6 pis. (Publ. 2561.) 

 A Pleistocene Cave Deposit in Western Maryland, by J. W. Gidley. G pp., 



pis. (Publ. 2562.) 

 Paleobotany : A Sketch of the Origin and Evolution of Floras, by Edward W. 



Berry. 118 pp., 6 pis. (Publ. 2563.) 

 The Direct Action of Environment and Evolution, by Prince Kropotkin. 18 pp. 



(Publ. 2564.) 

 The Law of Irreversible Evolution, by Branislav Petronievics. 11 pp. (Publ. 



2565. ) 

 The Fundamental Factor of Insect Evolution, by S. S. Chetverikov. S pp., 1 pi. 



(Publ. 25(56.) 



