274 
Journal of Agricultural Research 
Vol. VII, No. 6 
every case, however, the grain-forming material was dissolved upon 
treatment with water for 24 hours. There were left in the cells which 
had formerly contained the solid crystalline substance the scattered, 
single crystals and also frequently calcium oxalate sand crystals an 
idioblast of which had been included in the group of cells which became 
petrified through the deposit in them of the grain-forming substance. 
HYGROSCOPIC PROPERTIES 
In connection with the physical and chemical characteristics of the 
grain may also be mentioned the results of some determinations of the 
hygroscopidty of some of the component parts of the leaf procured by 
the mechanical process already described. For these determinations 
four classes of air-dry material were used: (1) the leaf web—that is, 
the soft, parenchymatous tissue which passed through a 200-mesh 
sieve; (2) large veins—that is, those which, excluding the midrib, would 
not pass through a 20-mesh sieve; (3) smaller veins, which passed through 
a 30—but not an 80-mesh sieve; and (4) grain, a mixture of various sizes. 
Two-gm. samples of each of these classes were exposed for 50 hours side 
by side in open, tared Petri dishes to an atmosphere containing moisture 
derived from 125 gm. of granulated cigar-filler tobacco containing 26 
per cent of moisture, a tight desiccator kept at about 30° C. being used as 
a container. The percentages of moisture absorbed by the samples were 
determined in the usual way, with the following results: Leaf web, 20 per 
cent; large vein, 17 per cent; small vein, 25 per cent; and grain, 14 per 
cent. 
The granulated tobacco was used as a source of moisture in order to 
produce, as nearly as possible, natural conditions and the greatest com¬ 
petition between the samples and also between these and the source of 
moisture, at the same time insuring against the condensation of moisture 
within the desiccator through changes in temperature. While these 
results are products of work of a preliminary nature, enough has been 
done to indicate that the grain is the least and the small veins the most 
hygroscopic of the kinds of material studied. In connection with the 
latter it is believed that their power to absorb so large an amount of 
moisture may be due, at least in part, to a colloidal substance present in 
some of their xylem or phloem elements. This substance has the property 
of swelling markedly and protruding from the ends of pieces of small 
veins when the latter are submerged in water. 
qualitative tests 
Qualitative tests of the pure grain and its ash showed an abundance 
of calcium, some potash and magnesia, and a little ammonia, but only 
traces of oxalic, nitric, and sulphuric acids, the last of which was proved 
to arise chiefly from the combustion of proteids in the process of ashing. 
