390 INDEX TO AMERICAN BOTANICAL LITERATURE 
Richards, H. M. Determination of acidity in plant tissues. Mem. 
Torrey Club 17: 241-245. 10 Je 1918. 
Robbins, W. J. Direct assimilation of organic carbon by Ceratodon 
purpureus. Bot.,Gaz. 65: 543-551. f. 1-5. 18 Je 1918. 
Robbins, W. W. Successions of vegetation in Boulder Park, Colorado. - 
Bot. Gaz. 65: 493-525. f. 1-14. 18 Je 1918. 
Rock, J. F. New species of Hawaiian plants. College Hawaii Publ. 
Includes Cyrtandra cyaneoides, Clermontia montis- ae C. Waimeae, Cyanea 
communis, Rollandia puirweerdisfolia; R. truncata, spp. ., and five new varieties. 
Rusby, H.H. Recent botanical collecting in the Republic of Colombia. 
Mem. Torrey Club 17: 39-47. 10 Je 1918. 
Ruthhoven, A. G. A biological survey of the sand dune region of the 
south shore of Saginaw Bay, Michigan. Michigan Geol. & Biol. 
Surv. Publ. 4: (Biol. 2) 1-347. pl. 1-15 + map. 1911. 
Scott, J. G. Early horticultural journalism in the United States. 
Mem. Torrey Club 17: 79-81. 10 Je 1918. 
Seaver, F. J., & Horne, W. T. Life-history studies in Sclerotinia. 
Mem. Torrey Club 17: 202-206. pl. 3. 10 Je 1918. 
Sclerotinia Geranii sp. nov. is described. 
Shaw, J.K. A study of variation in apples. Massachusetts Agr. Exp. 
Sta. Bull. 149: 21-36. Ap ro14. 
Shufeldt, R. W. Flowers of late spring and early summer. Am. 
Forestry 24: 289-294. f. 1-10. My 1918 
Spegazzini, C. Sobre algunos Hongos Chilenos. Rev. Chilena Hist. 
Nat. 21: 79-81. 30 Je 1917. 
Spegazzini, C. Uredinaceas nuevas chilenas. Rev. Chilena Hist. 
Nat. 14: 139, 140. I9gI0. 
Spoehr, H. A. The pentose sugars in plant metabolism. Plant World 
20: 365-379. D 1917. 
Steil, W. N. Method for staining antherozoid of fern. Bot. Gaz. 68: 
562, 563. f. r. 18 Je 1918 
Steinberg, R. A. A study of some factors influencing the stimulative 
action of zinc sulphate on the growth of Aspergillus niger. I. 
effect of the presence of zinc in the cultural flasks. Mem. Torrey 
Club 17: 287-293. 10 Je 1918. 
Stiles, W., & Jérgensen,I. Quantitative measurement of permeability. 
Bot. Gaz. 65: 526-534. 18 Je 1918. 
