624 WENT 



a whole range of positions from Assistant to Instructor, Assistant Professor to 

 full Professor does not make the latter stand out as a sort of half-god. 



In discussing special problems in plant physiology during the last 50 years 

 it is possible to use the book by Weevers, written to cover this same period, 

 but not restricted to America. 



In conclusion I want to mention some of the most outstanding achievements 

 of plant physiology in the U.S.A. during the last 50 years. As mentioned 

 earlier, plant nutrition was one of the subjects receiving early attention, 

 largely because of its practical significance. But the contributions to this 

 field by American physiologists soon surpassed the merely practical aspects. 

 Probably most significant was the group of investigators which Hoagland or- 

 ganized in the College of Agriculture of the University of California in 

 Berkeley. There the uptake of ions by the plant was studied from all possible 

 angles, and for the last quarter century much of the progress in the field 

 of plant nutrition was spearheaded by Hoagland's group, among whom I 

 would like to mention Davis, Arnon, Stout, Barker, Jenny, Hassid, Broyer, 

 and Ulrich, with F. C. Steward and others as visiting scientists. The recog- 

 nition of zinc, molybdenum, and chlorine as essential elements in the nutrition 

 of plants was due to teamwork, possible through the American genius of 

 organization embodied in Hoagland, which leaves full room for personal ex- 

 pression yet integrates the individual efforts into something greater than the 

 arithmetical sum of the contributions. Other laboratories have also contributed 

 significantly to the problem of plant nutrition, such as the Rutgers group 

 under Shive and the U.S. Salinity Laboratory in Riverside. 



Problems of ion uptake by cells were studied in other directions also, e.g., 

 by Osterhout and Blinks in connection with bioelectric potentials, by Brooks 

 and Jacobs using the animal cell as a starting point, and by Thimann and 

 Bonner and coworkers, employing the effects of auxins on water and ion up- 

 take, and by F. C. Steward in connection with protein synthesis. 



Another problem which received much attention in the early days of 

 American plant physiology was that of water relations of plants. The investiga- 

 tions of Briggs and Shantz in this field are fundamental in determining the 

 wilting percentage of soils in relation to crop plants and in measuring total 

 water loss. From this work stemmed the development of the lysimeter. Living- 

 ston's name will always remain connected with his atmometer, providing a 

 physical measurement of evaporative power, which can be directly compared 

 with plant transpiration. Books like those by Crafts and Currier and by 

 Kramer testify to the continued interest in these problems in the U.S.A. 



Seed physiology was studied in the early days by Crocker and Shull, at the 

 University of Chicago, and from this work the predilection of American 

 physiologists for the lowly cocklebur {Xanthium) stems. When Crocker 

 organized the Boyce Thompson Institute for Plant Research, germination 

 problems remained among the favorite research problems which are sum- 



