A478 Philippine Journal of Science 1920 
not require a very high partial concentration of oxygen in the 
solution in which they are growing, since these plants thrive 
excellently when rooted in mud containing large amounts of 
organic matter (reducing agents). No special method was em- 
ployed to aérate the solutions in the tests here considered, but 
it may be assumed that all cultures were about alike in this 
regard and that the supply of oxygen to the root surfaces 
was considerable. The solutions were of course exposed to 
the air, for the corks bearing the seedlings were far from air- 
tight. That good growth was obtained in some cultures indi- 
cates that the oxygen supply was adequate, at least with ref- 
erence to the non-oxygen conditions employed. With more or 
less rapid supply of oxygen to the roots, and possibly with 
other solution and non-solution conditions than those here giv- 
ing best growth, it is of course possible that still better growth 
might be obtained. No attempt was made to study the influence 
of oxygen partial concentration in the media used in these ex- 
periments. 
From the preceding paragraphs it is clear that the solution 
conditions (salts, salt proportions, total concentration, oxygen 
partial concentration, as well as the partial concentrations of 
excreted substances) altered in some unascertained manner from 
the time the seedlings were placed in the culture bottles to the 
time of the first renewal of the solution. At the time of renewal 
the solution conditions were suddenly brought back to the state 
in which they were at the beginning of the culture. Then al- 
teration began once more and continued for three or four days, 
when these conditions were again brought back to standard. 
The standardization of these conditions was subsequently re 
peated at intervals of three or four days till the end of the culture 
period. 
No attempt was made to determine how the solutions changed 
between renewals. The line of study here suggested has at- 
tracted considerable attention in the past and will surely be 
continued by plant physiologists, but it has not yet been applied 
to rice in any thorough manner. 
THE NON-SOLUTION CONDITIONS OF THE ENVIRONMENT 
By non-solution conditions of the surroundings are here meant 
all those conditions that may have influenced the growth of these 
plants, excepting the conditions that are determined directly by 
the salts, salt proportions, and total concentration of each culture 
solution. These non-solution conditions of the evironment we 
