5 



CONTENTS. 



Page 



List of illustrations v 



Introduction 3 



I. Investigations at Peru, Nebraska, in 1919. 



University No. 21 oats, Avena sativa 8 



Swedish Select oats, Avena sativa 11 



Durum wheat, Triticum durum 13 



Marquis wheat, Triticum cestivum 15 



Manchuria barley, Hordeum vulgar e 18 



Corn, Zea mays indentata 21 



Earlier investigations of corn 25 



Potato, Solanum tuberosum 26 



Earlier investigations of potatoes 29 



Comparison of root systems 30 



Environmental conditions of growth 32 



Summary of root development 38 



II. Investigations at Lincoln, Nebraska, in 1919 and 1920. 



Oats, Avena sativa 41 



Barley, Hordeum vulgare , 48 



Wheat, Triticum cestivum 49 



Alfalfa, Medicago sativa 52 



Sweet clover, Melilotus alba 54 



Comparison of root systems 55 



III. Investigations at Phillipsburg, Kansas, in 1920. 



Oats, Avena sativa 57 



Barley, Hordeum vulgare . . . . | 59 



Wheat, Triticum cestivum . . . . 59 



Alfalfa, Medicago sativa 60 



Sweet clover, Melilotus alba. . 60 



Summary of crop development 60 



IV. Investigations at Burlington, Colorado, in 1920. 



Wheat, Triticum cestivum 62 



Oats, Avena sativa 67 



Barley, Hordeum vulgare 68 



Alfalfa, Medicago sativa 69 



Sweet clover, Melilotus alba 70 



Summary of crop development 71 



Summary of environment and crop development at all stations, 1920 72 



V. Investigations at All Stations in 1921. 



Investigations at Peru, Nebraska 78 



Investigations at Lincoln, Phillipsburg, and Burlington 80 



Summary of environment and crop development 87 



Correlation of crop development with that of native vegetation 89 



VI. Depths at which Plants absorb Water and Nutrients. 



Preliminary experiments 93 



Field experiments, 1920 94 



Greenhouse experiments, 1920-21 100 



Field experiments, 1921 105 



Summary 114 



Bibliography 110 



in 



