140 INDEX TO AMERICAN BOTANICAL LITERATURE 
Richards, H. M. Gas interchange in Mesembryanthemum and, other 
succulents. Carnegie Inst. Washington Year Book 16:79, 80. 1917. 
Rickett, H. W. A quantitative survey of the flora of Lake Mendota 
[Wisconsin]. Science II. 52: 641, 642. 31 D 1920. 
Rusby, H. H. Descriptions of three hundred new species of South 
American plants. Pp. 1-170. 20 D 1920. New York. 
Contains also an index to previously published South American species by the 
same author. 
[H. H. Rusby]. The Mulford biological exploration of the Amazon 
basin. Am. Jour. Pharm. 92: 815-820. N 1920. - 
Sampaio, A. J. de. A seccado de Botanica no primeiro seculo de exis- 
tencia do Museu Nacional. Arch. Mus. Nac. Rio Janeiro 22: 
37-47-1919. 
Schneider, C. Notes on American willows. X. Jour. Arnold Arbor. 
2: 65-90. ; 1920. 
Includes 1 new variety and 2 new combinations. 
Seifriz, W. Viscosity values of protoplasm as determined by micro- 
dissection. Bot. Gaz. 70: 360-386. 24 N 1920. 
Setchell, W. A. Geographical distribution of the marine spermato- 
phytes. Bull. Torrey Club 47: 563-579. 28 D 1920. 
Sherff, E. E. North American species of Taraxacum. Bot. Gaz. 70: 
329-359. pl. 31-33. 24 N 1920. 
Shreve, E. B. The relation between water loss by evaporation and 
water gain by absorption in colloidal gels. Carnegie Inst. Wash- 
ington Year Book 16: 68-71. 1917. 
Shreve, E. B. The transpiring power of plants. Carnegie Inst. 
Washington Year Book 16: 67, 68. 1917. 
Sifton, H. B. Some characters of xylem tissue in cycads. Bot. Gaz. 
70: 425-434. pl. 37, 38 +f. 1. 30 D 1920. 
Silveira, A. A. da. Algumas especies novas da flora de Minas Geraes. 
Arch. Mus. Nac. Rio Janeiro 22: 99-103. pl. oats 1919. 
Includes new species in Chusquea, Arundinaria and Bom 
Small, J. K. A botanical excursion to the Big ty Nat. Hist. 
20: 488-500. O 1920. [Illust.] 
Soth, B. H. The alpine spring beauty. Am. Bot. 26: 115. N 1920. 
Spoehr, H. A. The carbohydrate economy of cacti. Carnegie Inst. 
Washington Year Book 16: 73-79. 1917. : 
dley, P. C. A new species of Campnosperma from Panama. 
Jour. Arnold Arbor. 2: 111, 112. 1920. 
