SKOOG AND TSUI 285 



12. Thimann, K. v., Skoog, F., and Byer, A. C, ibid., 29:598-606 (1942). 



13. Thimann, K. V. and Sweeney, B. M.,J. Gen. Physiol., 21 :i23-i35 (1937)- 



14. White, P. R., Am. J. Botatiy, 26:59-64 (1939). 



15. , Bull. Tor. Hot. Club, 66:507-513 (1939). 



16. Zarudnaya, Katerina, The effect of pH on growth of tobacco callus 



tissue cultures. M.A. thesis, Johns Hopkins University, 1945. 



