May 7.1917 Citrus Leaves at Various Stages of Mottling 161 
In the healthy leaves and usually also in the less mottled leaves of 
both orange and lemon the percentage of each mineral element is less 
in the midrib than in the mesophyll tissue. In leaves in the last stage 
of mottling, however, there is no definite uniformity in this respect, the 
midrib containing in some cases a higher and in some cases a lower 
percentage than the leaf proper. There does not appear to have been 
any difficulty about the transfer of these mineral elements from the 
conducting tissue to the mesophyll areas. 
In most cases, regardless of the stage of mottling, the leaf stems con¬ 
tain less iron, calcium, and magnesium than either the midrib or meso¬ 
phyll. The phosphoric add is more evenly distributed in the three 
portions of the leaf. 
. Table II shows the results of analyses of orange leaves collected from 
a commercial grove near Riverside. There was decidedly less calcium 
and a little less magnesium in the leaves in the medium stage of mottling 
than in the healthy leaves or in the worst mottled leaves; otherwise, the 
remarks regarding the leaves discussed from Table I apply to those 
given in Table II. 
Tab II .—Composition of orange leaves in various stages of mottling . Leaves col¬ 
lected on April 18, igi6 
Part analyzed. 
Stage of 
mottling. 
Percentage distribution. 
Percentage on dry substance. 
Fe. 
Ca. 
Mg. 
P2O6. 
Fe. 
Ca. 
Mg. 
P2O5. 
Leaves minus midribs. 
None . . . 
39 
44 
40 
39 
0. 0126 
2. 88 
O. 261 
0.436 
Midribs alone... 
...do. 
39 
3<5 
33 
33 
. 0126 
2-35 
. 214 
.368 
Leaf stems. 
22 
20 
27 
28 
.0075 
i -35 
• 173 
.308 
Average of leaves 
and midribs ... 
.0126 
2. 62 
. 238 
. 402 
Leaves minus midribs. 
2-3 
48 
40 
4 i 
38 
. 0250 
1. 96 
. 242 
• 455 
Midribs alone. 
2-3 
32 
35 
3 i 
32 
. 0167 
i- 73 
.183 
• 376 
Leaf stems. 
2-3 
20 
25 
28 
30 
.0105 
1. 27 
• 159 
.360 
Average of leaves 
and midribs. . . 
. 0209 
i.8 S 
.•213 
. 416 
Leaves minus midribs. 
3-4-5 
26 
34 
37 
3 i 
.0185 
3* 22 
.294 
. 400 
Midribs alone. 
3-4-5 
29 
42 
36 
35 
.0200 
4- 05 
.285 
.450 
Leaf stems . . .. 
3-4-5 
45 
24 
27 
34 
.0316 
2. 28 
. 220 
.430 
Average of leaves 
, 
and midribs. .. 
.0193 
3-64 
. 290 
.425 
The leaves reported in Table III were collected on January 3, 1916, 
in commercial groves near Riverside. These leaves, except the last set 
given, were collected from the same grove; usually the healthy and 
mottled leaves 3 were taken from the same tree branches, where both 
