456 Philippine Journal of Science 192 
only does not supply the mineral salts needed by the plant, but 
it also acts to remove salts already within the plant body. The 
study to be reported in this paper deals with the growth of 
young rice plants (Oryza sativa, variety ‘““Wateribune”) in aque- 
ous solution cultures. No attempt will be made here to review 
studies made on culture solutions, but the readers are referred 
to Tottingham’s* monograph which gives a very complete re- 
sumé of earlier solution-culture experimentation with plants and 
to later papers that appeared on the subject. A brief review, 
however, will be made of previous studies on rice which appear 
to have a direct bearing on the present problem. | 
REVIEW OF PREVIOUS EXPERIMENTS ON THE MINERAL NUTRITION 
OF RICE 
The present studies deal with solution cultures, as has been 
said, and they may serve as a small contribution toward a bet- 
ter knowledge of this field of physiology. Such studies, how- 
ever, must of course involve some particular kind of organism 
and the rice plant was chosen as the experimental subject, for 
several reasons. In the first place, it seemed that the extensive 
aspect of our knowledge of this phase of physiology deserved 
attention; there are so many different sorts of plants, and gen- 
eralizations for all plants are perhaps too easily formed from 
knowledge of a few kinds. The aim was to select a plant that 
would probably show some important physiological differences 
from the ones thus far studied. At the same time the plant 
used should be one of considerable human interest, for plant 
production and the practical applications of plant physiology 
are always demanding more scientific knowledge than is avail- 
able. These studies were to be purely physiological, but the 
plant used might well be one of agricultural interest. Also, of 
course, the plant selected must be suited to solution-culture 
experiments; soils, and even sand cultures, present problems 
that are so complicated as to be almost hopeless until some of 
the simpler problems offered by solution cultures become bettet 
understood. Choosing the experimental subject at a time when 
agricultural operations loomed very large on the world’s horizon, 
when the whole of civilization was in the tightening grip of a 
quasi famine, it was natural first to consider what plants are 
*Tottingham, Wm. E., A quantitive chemical and physiological study 
of nutrient solutions for plant cultures, Physiol. Res. 1 (1914) 133-245. 
See also Shive, J. W., The freezing points of Tottingham’s nutrient solu- 
tions, Plant World 17 (1914) 345-353. 
