May 7, i9i7 Citrus Leaves at Various Stages of Mottling 163 
but there does not seem to have been any definite accumulation of these 
elements in the midribs, with the exception of phosphoric acid. The 
average percentage of the various elements in the whole leaf is about the 
same as in the other leaves reported in Table III. 
Table IV shows a comparison of the composition of old and new leaves 
of grapefruit {Citrus decumana ). The difference in the calcium and the 
magnesium contents is striking, though the amount of phosphoric acid 
is about the same in the old and new leaves. The results show the 
importance in a study of this kind of securing leaves of as nearly the same 
stage of development as possible. 
Table IV .—Analysis of old and new grapefruit leaves. Collected on January 3, igi6 
Percentage distri- 
Percentage on dry sub- 
bution. 
stance. 
Part analyzed. 
Description. 
Ca. 
Mg. 
P2O5. 
Ca. 
Mg. 
PaOs. 
Leaves minus midribs. .. 
Old leaves under 
49 
48 
5 2 
5. 06 
0.425 
o -455 
the new leaves 
given below. 
. 416 
Midribs alone /. 
.do.. 
51 
5 2 
48 
5 - 24 
.471 
Average. 
5-15 
.448 
• 436 
Leaves minus midribs. .. 
New leaves above 
47 
56 
57 
2.13 
*332 
. 560 
the old leaves 
given above. 
. 260 
Midribs alone. 
.do. 
53 ’ 
'44 
43 
2.41 
.431 
* 
Average. 
2. 27 
. 296’ 
.496 
Table V shows the analyses of leaves from a privet plant (Ligustrum 
aurea) growing in White Park, Riverside, Cal. A number of branches 
produced in part leaves which were light yellow or almost white in color. 
The percentage of calcium was found to be considerably greater in the 
green leaves than in the yellow leaves. The percentage of magnesium 
was greater in the green leaves, while the percentage of iron and of 
phosphoric acid was greater in the yellow leaves, indicating that the 
absence of chlorophyll is not likely to be due to lack of iron or phosphoric 
acid. The leaf stems of the yellow leaves contain more of each of the 
elements determined than the leaf stems of the green leaves, which might 
be interpreted to indicate that the transfer of mineral nutrients did not 
take place as freely from the leaf stems in the yellow branches as in the 
green ones. 
In the last set of analyses of privet leaves given in Table V, the 
yellow margins also contained more iron and phosphoric acid than the 
green midribs, but about one-half as much calcium and a little less 
magnesium. Of the two elements necessary for chlorophyll formation, 
iron and magnesium, iron is present in larger amounts in the yellow 
