Acknowledgment is made for permis- 

 sion to reproduce certain copyrighted 

 material, as follows: Williams and Wil- 

 kins Co. (Soil Science), Tables 1, 2; 

 Text figures 4, 17, 31, 34, 42, 43, 44; 

 Plate 20; Rockefeller Institute (Journal 

 of General Physiology), Text figures 12, 

 14, 15, 24; Long Island Biological Asso- 

 ciation (Cold Spring Harbor Symposia), 

 Text figures 39, 41. 



