16,6 Espino: Salt Requirements of Young Rice Plants 435 
solutions differences in the appearance of the plants generally 
began to be manifest and these differences became more striking 
as the cultures became older. With higher total concentrations 
these differences became pronounced sooner than with lower 
total concentrations. All of the cultures of series 14 to 22 inclu- 
sive gave better plants than were obtained in distilled-water 
cultures simultaneously carried out; the lowest total concentra- 
tion tried (series 14, 0.0008 gram-molecule per liter, or 0.04 
atmosphere) gave better growth in all of its salt proportions 
than did distilled water. Of the six total concentrations tested, 
it was generally true that the plants grew faster at first in the 
weaker solutions, but after about ten days of growth some of the 
cultures having the second or third total concentration (series 
15 and 16, 0.0016 gram-molecule or 0.08 atmosphere, and series 
17, 18, and 19, 0.0038 gram-molecule per liter, or 0.2 atmosphere) 
showed the most rapid growth. 
Most of the cultures with the three weaker total concentrations 
gave good growth, and the best plants of these series were much 
better in appearance than were the best ones obtained in any 
of the 3-salt series with rice. There was generally some drying 
of the tips of the leaves, especially in the first half of the culture 
period, and this feature was developed more strongly as the 
total concentration was higher ; but it appeared not to be related 
to salt proportions, for it was about the same for all. While 
the dead regions of the leaf tips were only about 0.5 centimeter 
long with the lowest total concentration used, they were two or 
three times as long with the fourth of the total concentrations 
(series 20, 0.0077 gram-molecule per liter, or 0.40 atmosphere) . 
The best cultures of series 14 to 20 (with the four lower con- 
centrations) showed good color and the plants were apparently 
normal in every way. 
The highest two total concentrations (series 21 and 22, 0.0192 
and 0.0384 gram-molecule per liter, or 1 and 2 atmospheres, re- 
spectively) gave poor growth with all salt proportions, the plants 
appearing markedly stunted, and the leaves drying badly at the 
tips or even so far as to affect nearly the whole blade. Chlorotic 
leaves were common with these two stronger total concentra- 
tions. For these two series no quantitative plant measurements 
were made, and they will not be considered in the sections that 
follow. 
In connection with this observation that the highest two con- 
centrations tested showed no sets of salt proportions at all suited 
to the growth of these plants, it is of interest to emphasize the 
