466 
Philippine Journal of Science 
1920 
of salt proportions and a number of different total concentrations 
of this 4-salt type of nutrient solution were tested, and certain 
ones of these proved to be excellent for the plants employed. 
The question then arose, whether the presence of the nitrate 
ion in the medium might not be either unnecesary or even posi- 
tively harmful to the young rice plants, and the third stage of 
these studies dealt with still another 4-salt type solution, which 
contained all the generally necessary mineral elements but con- 
tained no nitrate. Nitrogen was supplied here only as ammo- 
nium sulphate. This type of solution was also tested with many 
different sets of salt proportions and with a number of different 
total concentrations. The results showed that some of these 
solutions gave very good general growth, but the best of them 
were not as good as the best ones containing nitrate; this type 
of solution always produced a characteristic leaf injury. 
The work here reported was carried out in the Laboratory 
of Plant Physiology of the Johns Hopkins University; and the 
writer’s acknowledgments and thanks are hereby expressed for 
the facilities of that laboratory, and for instruction, advice, and 
guidance given him by Prof. B. E. Livingston and Dr. H. E. 
Pulling. , 
EXPERIMENTATION 
SEEDS AND SEEDLINGS 
The rice used in this study was kindly furnished by the 
United States Department of Agriculture. It is of the lowland 
type bearing the name “Wateribune,” and this stock of seed 
was grown, under irrigation, at the Crowley Station of the 
Louisiana Agricultural Experiment Station. This variety is 
often grown on a small scale without irrigation in the South- 
eastern States, but always with very moist soil. 
In starting an experimental series, about two thousand seeds 
were first placed in about 300 cubic centimeters of tap water 
in an open glass pan (15 centimeters in diameter), where they 
were allowed to soak for twenty-four hours. They were then 
placed between folds of wet absorbent paper (paper toweling, 
about like thin filter paper), where they remained another 
twenty-four hours. At the end of this period germination was 
visibly beginning so that the plumule protruded slightly. The 
germinating seeds were next distributed on a net of paraffined 
cotton threads (mosquito netting, mesh about 1.5 millimeters 
square), which was stretched horizontally over the opening of 
a cylindrical earthen jar (55 centimeters in diameter and 40 
