226 BOTANICAL GAZETTE [SEPTEMBER 
of this extract were then made up to contain 300, 500, 700, 1000, and 
2000 parts per million of P,O, in the form of Na,HPO,. 
The plants were set in small wire baskets (paraffined along the sides 
only) containing some sterile quartz sand, and the baskets placed in jars 
containing the proper extract, as shown in figs. r and 2. One set of plants 
was prepared with the roots immersed in the liquid, another with roots 
remaining in the sand The cultures were aerated by pouring the liquid 
from one jar into another and the losses by evaporation and transpiration 
were made up daily with the corresponding extracts. The effect is seen 
in soil extract; . 
1G. 2.—Tolerance of wheat seedlings to solutions of NasHPO, il); 
roots kept in sand of the baskets: 1, distilled water; 2, soil extract (2 water: ? pr 
me . 
+ 1000? 
3, extract+rooPP™ P,O,; 4, same+sooPP™; 5, same+700PP™; 6, sa 
7, Same + 2000PP™_ 
from the photographs. Up to the 7ooPP™? concentration there w4® a 
marked difference between the two lots of plants. But while 700" 
immersed plants had a decidedly sickly appearance, the non-imme 
ones looked quite healthy even in the 1000?P™ extract. The 2000PP™ of the 
non-immersed lot kept on struggling along even after three weeks from 
planting; while the immersed ones were killed in less than ten days. t 
It is thus seen that even the sterile quartz enables the plants to oe 
higher concentrations of the phosphates. The actual amount of 
? Parts per million. 
