1921] SCHERTZ—MOTTLING 93 
per cell was formed in the cortex and in the pith. In the plant 
with mottled leaves 2 or 3 crystals were formed in each pith cell 
of the stem. Magnesium was also present in the xylem, phloem, 
cortex, and epidermal cells. 
In making comparative tests of the leaves for calcium, appar- 
ently a few more calcium sulphate crystals were formed in the 
cells of the mottled than the green leaves. In the green leaves 
much calcium was found in the epidermis of the petioles, some in 
the xylem and phloem regions, and little in the parenchyma. The 
same was true of the mottled leaves. In the stems many calcium 
sulphate crystals were formed in the pith cells on the addition of 
H,SO,. If there was any difference, more crystals were formed in 
the stems of the mottled plants. Calcium sulphate crystals were 
also formed in the xylem, phloem, cambium, and cortical regions. 
The fact that the mottled leaves and stems were always older than 
the green leaves and stems. of the same plant would account for 
more crystals being formed in their cells. 
In testing for phosphates by the addition of ammonium and 
magnesium chloride, only a very few crystals of ammonium mag- 
nesium phosphate were formed in the green leaves or in the mottled 
ones. Evidently the phosphorus must have been in some organic 
form in which it is not readily reactive with the reagents used, 
hence no conclusion can: be drawn from this test regarding the 
metabolic disturbances which may be produced by it. 
The test for nitrates gave the most interesting result. All 
of the green leaves gave tests which showed that an abundance 
of nitrate was present, while no positive results were obtained 
from the completely mottled leaves. It is of value to compare the 
progress of the mottling of the leaf with the absence of nitrates. 
The first signs of mottling usually appeared at or near the lobes of 
the leaf, and it was here that the test for nitrates was first negative. 
At this stage the greatest amount of nitrates was found in the con- 
ducting tissues of the leaf. Also in the deepest green leaves the 
conducting tissues contained the most nitrate. As the green 
disappeared from the tip of the leaf, more and more nitrates were 
found only in the veins close to the base. At this stage only a 
little greenish tint remained in the leaves. Usually as long as the 
