1921] SCHERTZ—MOTTLING 101 
cited by PALLADIN 41), who believe that the absolute amounts of 
phosphoric acid do not diminish as the season progresses. The 
writer must agree with Scuuize and Scniitz, who find that the 
phosphoric acid content decreases as the leaves age or as autumn 
approaches. 
Further evidence for the correctness of these views is presented 
by Tucker and Totiens (49), who have shown that phosphorus 
decreased markedly in the leaves of the plane tree on or about 
October 8. The amount of phosphorus in the leaves at the end 
of the growing season was less than 50 per cent of that found in 
the leaves during the earlier part of the year. They believe that 
the three plant nutrients (nitrogen, phosphorus, and potash) 
TABLE IX 
PROTEIN NITROGEN 
Sampl Sample Sampl vex 
e 
i ag no. ir no. III Average secsee aie: 
dry weight 
MOOR ss ersivs oe Sarees 0.189 0.243 ©. 207 0.213 3.35 
Bete 4A 0.076 0.080 0.087 0.081 1.39 
POG Be 0.073 0.064 0.079 0.072 1.14 
passed from the leaves into the stems as the leaves aged, and were 
not washed out by rains. 
Protein nitrogen was determined by the Gunning-Arnold modi- 
fication of the Kjeldahl process. In each case 10 gm. samples of 
the fresh leaves were used, and the results as given in table IX are 
grams of nitrogen per roo gm. of fresh leaves. 
The green leaves contained 1.33 per cent protein (N X6.25), 
while the mottled leaves contained 0.51 per cent, and those on 
poor soil B 0.45 per cent, when calculated on the wet weight of 
the leaves. Based on the weight of the dry leaves, the green ones 
contained 20.9 per cent, the mottled A contained 8.7, and B 7.13 
per cent protein. Parzaprn found considerable variation in the 
percentage of total nitrogen and protein nitrogen between etiolated 
and green leaves of various plants, but the difference was not 
always in the same direction. Orro and Kooper, and LECLERC 
DU SABLON (19) found that leaves decrease in their protein content 
