EARLY PROBLEMS 



27 



7. Kunkel, L. O., "Studies on aster yellows," Atner. J. BoL, 13:646-705 (1926); 



also in C. B. T. /., 1 : 181-240 (1926). 



8. , "Studies on aster yellows in some new host plants," C. B. T. I., 3 : 85-123 



(1931). 



9. , "Heat treatments for the cure of yellows and other virus diseases of peach," 



Phytopath., 26 : 809-830 (1936). 



10. Lojkin, Mary E., and Helen Purdy Bealc, "A colorimetric method for the quantita- 



tive determination of minute amounts of tobacco-mosaic virus and for the differ- 

 entiation between some of its strains," C. B. T. I., 13 : 337-354 (1944). 



11. Manns, T. F., "Peach yellows and httle peach," Delaware Agric. Exp, Sta. Bull. 236, 



50 pp. (1942). 



12. Meyer, Bernard S., Frank H. Bell, Lawrence C. Thompson, and Edythe I. Clay, 



"Effect of depth of immersion on apparent photosynthesis in submersed vascular 

 aquatics," Ecology, 24 : 393-399 (1943). 



