INDEX TO AMERICAN BOTANICAL LITERATURE 229 
Rowlee, W. W. The genus Cestus in Central America. Bull. 
Torrey Club 49: 283-292. pl. r2-15. 11 O 1922. 
Rudolfs, W. Effect of seeds upon hydrogen-ion concentration 
of solutions. Bot. Gaz. 74: 215-220. 16 O 1922. 
Rugg,H. G. Adiantum pedatum var. aleuticum in New England, 
Am. Fern Jour. 12: 128-130. pl. 8. 30 D 1922. 
Rusby, H. H. New species of trees of medical interest from 
Bolivia. Bull. Torrey Club 49: 259-264. 22S 1922. 
Includes new species in Nectandra (1), Ocotea(1),Aerodiclidium (1), 
and Guarea (2). 
Rusby, H. H. Report of work on the Mulford Biological 
exploration of 1921-22. Jour. New York Bot. Gard. 23: 
IOI-112. Au 1922. 
Exploration in’Bolivia and Brazil. 
Rusk, H.M. Lilium Warleyense. Addisonia 7: 57, 58. pl. 253. 
30 D 1922. 
Rydberg, P. A. Ambrosiaceae. N. Am. Fl. 33: 3-44. 15S 
1922. 
Includes Leuciva, Chorisiva, Acanthambrosia, gen.nov., and 18 new 
species. 
Rydberg, P. A. Carduaceae. N. Am. FI. 33: 45, 46. 15 S 
1922. 
Rydberg, P. A. Carduales. N. Am. Fl. 33:1. 15 S 1922. 
Sargent, C. S. Notes on North American trees, IX. Jour. 
Arnold Arb. 3: 1-11. Jl 1921. 
Includes 11 new species of Crafaegus. 
Sargent, C. S. Notes on North American trees, X. Jour. 
Arnold Arb. 3: 182-207. D 1922. 
Includes 25 new species of Crataegus. : 
Schaffner, J.H. The sexual nature of vegetative or dichotomous 
twins in Arisaema. Ohio Jour. Sci. 22: 149-154. Ap 1922. 
Schenck, H. Vegetationsbilder aus der Sierra de Mixteca, 
Mexico. Vegetationsbilder 14: pl. 25-36 with text. 1922. 
