506 
Philippine Journal of Science 
1920 
cium nitrate, and the high values in these triangles correspond 
to high partial concentrations of magnesium sulphate and low 
ones of the calcium salt. 
Considering each set of salt proportions singly, it is seen 
from Table 11 that the highest green weight most generally 
occurs with the low-medium total concentration (series 16) ; this 
is true for 20 out of the 35 sets of salt proportions tested. Of the 
remaining 15 sets, 7 show the highest green weight for the high- 
medium total concentration (series 19), and in all other cases 
(8) the highest value occurs for the lowest total concentration 
(series 14) ; in no case does the highest total concentration 
(series 20) give the highest green- weight value. This supports 
the conclusion reached from the study of the dry yields of tops 
and roots, that both of the medium concentrations are to be con- 
sidered relatively good for these plants, but that the low-medium 
total concentration is probably to be regarded as more nearly 
optimal than the high-medium. The last point is more strongly 
emphasized here than in the case of dry yields. 
Green weight of tops has frequently been employed as a cri- 
terion for comparing the physiological efficiencies of different 
environmental complexes, although it does not appear to have 
been used by earlier workers with solution cultures arranged 
for a thorough study of salt proportions. Since green weight 
consists, in any case, of the corresponding dry weight plus the 
corresponding water content, it is quite possible that the green- 
weight criterion (or the water content per weight unit of dry 
yield, or per weight unit of green weight itself) may bring out 
other physiological relations than those shown by the dry-yield 
criterion. For example, with a given total concentration, one 
set of salt proportions may give a higher dry-yield value than 
is given by another set, or the two sets may give equal values, 
and at the same time the first set may give a percentage of water 
content either less, equal to, or greater than that given by the 
other set. The salt proportions may influence not only the dry- 
yield production but also (possibly in an entirely different man- 
ner) the power of the plant to retain water. Two plants may 
have the same dry weight but may be markedly different phy- 
siologically (and in regard to commercial value), according to 
the amount of water retained in their tissue ; one might be much 
more succulent than the other, etc. Such possibilities are sug- 
gested in the literature. 
On account of these considerations it will be valuable to make 
a comparison between the indications of the dry-yield and of 
