X 



Introduction 



E. Melchers for figs. 8a, b, and c, Dr. Clinton for 

 figs. i6b, 38a and 40b, Professor R. E. Smith for fig. 

 22, Miss Nelly Brown for fig. 26, Professor A. D. 

 Selby for fig. 28a, Professor Edson for fig. 35, 

 Professor H. E. Stevens for figs. 37a and b, Profes- 

 sor H. S. Jackson for fig. 40a, Professor L. N. Mas- 

 sey for figs. 65b and 66a, Dr. A. B. Stout for fig. 

 72a, Professor Moznette for figs. 78c and d, The 

 King Construction Company for figs. 25 and 45, 

 The John Moninger Greenhouse Company for fig. 

 52, Professor F. B. Paddock for figs. 80 and 81. 



Credit is also due to the Foley Greenhouse Manu- 

 facturing Company for figs. 21, 49, 57a, 58a, 60 

 and 64. The remainder of the borrowed figures are 

 acknowledged in their proper places. The author 

 also wishes to express his indebtedness to the Texas 

 Agricultural Experiment Station for the original fig- 

 ures which were taken by the Station Photographer 

 for the Division of Plant Pathology and Physiology. 



J. J. Taubenhaus 



College Station, Texas 

 May 1, 1919 



