39 
influence of concentrated sulphuric acid upon the “grain.” Although 
there is some calcium oxalate present in the living leaf, the oxalic acid 
of those globules is produced by post-mortem oxidation, since they do 
not exist in the living leaf, the natural inference being that it is the 
oxidizing enzyms that produce them by inducing oxidation of various 
compounds, such as malic or citric acid, tannin, etc. The more oxidiza- 
ble material, and the more oxidation is going on in the tobacco. leaf, the 
more will the so-called grain develop in the curing and sweating proc- 
ess; hence it will in many cases, by no means in all, confirm the idea 
of some tobacco manufacturers that a well-developed grain is a good 
sign for the quality of the tobacco. 
The following observations by the writer may be mentioned: A fresh 
tobacco leaf was divided into two portions. One portion was hung up 
ina covered beaker containing some water, the other was first heated 
to 60° C. (140° F.) in a closed vessel before being thus treated. By 
the sudden killing of the cells by heat the cell sap left them at once 
and spread uniformly over the surface of the leaf, while in the former 
case the gradual drying and the later death diminish the migration of 
soluble matter to the surface. After eighteen days the “ grain,” in the 
form of numerous giobules of calcium oxalate, was formed in the nor- 
mally curing leaf, but not a trace of it was seen in the leaf killed imme-. 
diately after collecting it. This shows that these globular masses were 
formed in the curing process. In the fresh leaves deposits of calcium 
oxalate also occur aS mentioned, forming crystalline sandy deposits, 
especially in mesophyll cells. Generally these seem too small to account 
for the appearance of the “ grain” in cured and sweated leaves. 
The nature of the “ grain ” was also investigated by Dr. W. C. Stur- 
gis, who arrived at the same conclusion as the writer and at about the 
Same time. That author had the kindness to communicate the follow- 
ing observations: 
The crystalline deposits are insoluble in water, but are completely and readily 
soluble in dilute hydrochloric acid. On heating, these deposits swell to three or 
four times their original volume. Examination under the microscope of these 
heated masses in water, with the addition of hydrochloric acid, show that they are 
at once dissolved with copious evolution of gas. These observations, coupled with 
what we know of the occurrence of calcium oxalate in leaf tissues, lead me to con- 
clude that the grain of certain grades of tobacco is caused by the deposition in lim- 
ited areas of crystalline aggregations of this salt. © 
REMARKS ON THE DEVELOPMENT OF THE BROWN COLOR. 
The slow starvation process of the tobacco leaf in the curing barn is 
connected with the yellowing of the leaves, followed by the character- 
istic brown. The yellow color is chiefly due to the etiolating of the 
chlorophyll granules because of the absence of bright daylight, and 
sets in while the cells are still alive, while the brown color sets in after 
their death. The changes of the green to yellow and of the yellow to 
brown start and proceed generally in the same order, commencing 
at the margin and about midway between the lateral veins. Along 
