Dos +. INDEX TO AMERICAN BOTANICAL LITERATURE 
Nelson, J. C. Additions to the flora of western Oregon. Torreya 18: 
21-35. 8 Mr 1918. 
Osner, G. A. Additions to the list of plant diseases of economic im- 
portance in Indiana. Proc. Indiana Acad. Sci. 1916: 327-332. 
1917. 
Pammel, L. H., & Dox, A.W. The protein contents and microchemical 
tests of the seeds of some common Iowa weeds. Proc. Iowa Acad. 
Sci. 24: 527-532. 1917. 
Pipal, F. J. Weed seeds in the soil. Proc. Indiana Acad. Sci. 1916: 
368-377. 1917. 
Popenoe, W. Avocados as food in Guatemala. Jour. Heredity 9: 
99-107. f. I-4. Mr 1918. 
Porter, A. A., & Coons, G. W. Differences between the species of 
Tilletia on wheat. Phytopathology 8: 106-113. f. 1-4. Mr 1918. 
Rathbun, R. The Columbian Institute for the promotion of arts and 
sciences. U.S. Nat. Mus. Bull. ror: 1-85. 18 O 1917. 
h + 
chapters Botanical Gardens; Washington Botanical Society, etc. 
Rice, T. B. A study of the relations between plant growth and com- 
bined nitrogen in Winona Lake. Proc. Indiana Acad. Sci. 1916: 
333-362. f. I-16. 1917. 
- Rock, J. F. Pelea and Platydesma. Bot. Gaz. 65: 261-267. f. I. 
15 Mr 1918. 
Includes Pelea Gayana and P. recurvata, spp. nov. 
Rosendahl, C. O. Observations on Betula in Minnesota with special 
reference to some natural hybrids. Minnesota Bot. Stud. 4: 443- 
459. dl. 40 + J. 1, 2. 20°35 1616. 
Rosendahl, C. O., Observations on the morphology of the underground 
stems of Symplocarpus and Lysichiton, together with some notes on 
geographical distribution and relationship. Minnesota Bot. Stud. 
4: 137-152. BW. 24,22 © 1-17, 2, 18 5 1081. 
Rosendahl, C. O., & Butters, F. K Reputed Minnesota plants which 
probably do not occur in the state. Minnesota Bot. Studies 4: 461— 
473: 2058 1916. 
Sax, H. J. Spore formation in Philocopra coeruleotecta. Am. Jour. 
Bot. 5: 61-78. pl. 9-11. 9 Mr 1918. 
Schaffner, J. H. The expression of sexual dimorphism in heterosporous 
sporophytes. Ohio Jour. Sci. 18: 101-125. f. 7-28. F 1918. 
