286 
Journal of Agricultural Research 
Vol. VII, No. 6 
as had obtained near the outer edges of the leaves on the ninth day of 
curing. Examination after the same leaves had been fermented, how¬ 
ever, showed that the grain was much more pronounced on the surface, 
and the microscope revealed a greater degree of aggregation than had 
existed at the end of the curing process. It is believed that with the 
high water content of the fermenting tissue the grain substance is gradu¬ 
ally put in solution, particularly in the case of the smaller bodies, and 
that further grain aggregation and development of intervening zones of 
comparatively empty cells is thereby made possible. 
SUMMARY 
(1) The grain of cigar tobacco consists of hard bodies which, if suf¬ 
ficiently large, cause the surface of the leaf containing them to present a 
pimply appearance. This grain, in connection with other intimately 
related properties of the leaf, constitutes an important factor in deter¬ 
mining the value of cigar tobacco. 
(2) Each body consists of from one to several leaf cells distended with 
a mass of crystalline substance. They are most prominent microscopi¬ 
cally when examined with polarized light. Although visible in ordinary 
transmitted light, owing to the concentration in them of a large part of 
the brown coloring matter of the leaf, the details of their structure are 
more apparent when the former method of examination is used. 
(3) Based upon microscopic features, five forms or types of grain are 
recognized, though their significance is a matter still to be investigated. 
(4) Two other kinds of crystalline material are found in the tobacco— 
namely, cryptocrystalline calcium oxalate, contained in certain cells in 
the various tissues of the leaf; and single, small, prismatic crystals 
scattered evenly throughout the leaf, one in nearly every cell of the 
mesophyll and epidermis. 
(5) A mechanical method resulted in the separation of the grain bodies 
from the other portions of the leaf and gave an approximate mechanical 
analysis. This analysis showed roughly the percentages by weight of 
leaf web, veins, and grain. 
(6) Chemical analyses proved that the grain is composed chiefly of 
calcium, with a little magnesium and potassium, in combination with 
citric and malic acids rather than with oxalic acid. One of the salts, 
normal calcium malate, was identified by petrographic methods. De¬ 
terminations of the hygroscopic properties of the component parts of 
the leaf separated by mechanical means indicate that the grain is not 
responsible for the marked hygroscopic properties of tobacco, since it 
absorbed the least water from a moist atmosphere. The small veins 
showed the greatest hygroscopicity. 
(7) The grain bodies of tobacco are developed in the course of post¬ 
mortem changes which take place during the process of curing and con- 
