1921] SCHERTZ—MOTTLING 87 
all showed branches developing in axils of the leaves. The branch- 
ing was especially prominent in the plants watered with nutrient 
solution lacking iron. No branches developed on the plants 
watered with nutrient solutions lacking PO, or NO,. 
On August 1 (3 months after planting) the number of pairs of 
leaves still attached was counted and compared with the number 
of pairs which had fallen. The plants were similar when the 
experiment was begun. Each group contained 26 plants and the 
average of these was taken. 
Table IT shows that when phosphate or nitrate was lacking a 
greater percentage of the leaves fell compared with any other 
element. This may partially be accounted for because plants 
lacking NO, or PO, had a smaller percentage of new leaves, and 
TABLE II 
EFFECT OF NUTRIENT ON LEAF FALL 
ELEMENT LACKING 
LEAVES 
Fe Mg Ca PO, | NO; | None 
Average number of pairs 
dropped per plant...... 7 7 6 7 5 x 
Average number of pairs 
still attached........... 9 9 9 3 4 
Percentage dropped....... 45 45 49 7” 56 de 
consequently a smaller percentage of leaf fall. This did not account 
for the fact that when phosphate was lacking 14 per cent more of 
the leaves fell than when nitrate was lacking. The plants lacking 
Fe and those lacking Mg during the course of the experiment grew 
16 pairs of leaves; those lacking Ca and those on complete nutrient 
solution each grew 15 pairs of leaves; those lacking PO, grew 10 
pairs of leaves; and those lacking NO, grew only 9 pairs. 
To 8 of the plants (2.5 months old) which were grown in sand 
cultures with NO, or PO, lacking, one watering was made with a 
solution which contained the lacking element. The effect is 
shown in fig. 2. Two weeks after the watering the height of the 
treated plants was about twice that of those which had no nitrate 
or no phosphate added, and the area of the new leaves put forth 
was from three to four times the area of the old leaves below them. 
