100 BOTANICAL GAZETTE [FEBRUARY 
which took place in Coleus are of a similar nature to those accom- 
panying the yellowing of leaves in the autumn. Since the green 
and mottled leaves of Coleus were about the same size, and since 
there was only two or three weeks’ difference at the most in the 
ages of the leaves of Coleus, it is hardly possible that the differ- 
ences could be accounted for in any way except that the P.O; 
content actually decreased, and this would mean a transfer of 
materials from the leaf to the stem. If the amount of phosphorus 
were figured per leaf, then, since the leaves were about the same 
size, there would be nearly a 50 per cent reduction in the amount 
of phosphorus. Such a conclusion is in harmony with results 
from the cultures, for they showed that phosphate was necessary 
for growth of the plant, and when phosphates were deficient a 
larger percentage of the leaves fell. This conclusion is not out of 
TABLE VIII 
PHOSPHORIC ACID CONTENT OF LEAVES OF Acer Negundo 
Phosphoric acid May 7 June 6 July 5 | August 2 |September 3| September 25 
Percentage dry weight..| 1.500] 0.801 | 0.705 | 0.580 | 0.586 0.333 
Grams per 200 leaves...| 0.256 | 0.200] 0.210 | 0.134] 0.147 0.099 
P.O, as percentage of ash} 20.8 10.7 8.8 6.3 6.2 2.9 
harmony with the work of Scuu1ze and Scutirz (44). In working 
on Acer Negundo these investigators showed that the phosphorus 
content decreased gradually and quite definitely from May to 
September, whether the phosphorus content was calculated as 
percentage of dry weight, grams per 200 leaves, or calculated from 
the ash. Only the results of their work on leaves collected in the 
morning will be given here, as they are most directly comparable 
with those of the writer, yet it is worthy of note that nearly always 
the phosphorus content of the leaves in the evening was greater 
than in the morning. This seems to indicate storage and synthesis 
during the day and a loss of phosphorus compounds during the 
night. The phosphoric acid content of the leaves is summarized 
in table VIII. 
This work shows that the amount of phosphoric acid in the 
leaves of Acer Negundo decreases as the season advances. From 
these data one cannot agree with WrHMER or RIESMULLER (as 
