RECENT WORK IN AGRICULTURAL SCIENCE. 



AGKICULTURAL CHEMISTRY— AGROTECHNY. 



Giain of the tobacco leaf, C. S. Ridgway {U. S. Dept. Agr., Jour. Agr. Re- 

 search, 7 (1916), No. 6, pp. 269-288, pis. 3, figs. 2).— The results of the study re- 

 ported show that the bodies which cause the grain in cigar tobacco consist of 

 from one to several leaf cells filled with a crystalline substance. These bodies 

 are microscopically visible in ordinary transmitted light, but are more prominent 

 when examined with polarized light. Five forms or types of grain were recog- 

 nized, but their significance was not Investigated. Cryptocrystalline calcium 

 oxalate contained in certain cells in the various tissues of the leaf and single 

 small prismatic crystals scattered evenly throughout the leaf were also 

 identified in the tobacco. 



The grain was separated from the leaf by a process of mechanical analysis 

 described in detail. Incidentally in the sepai'ation of the grains it was found 

 that, using a sample of 70 gm., 33 per cent of the weight represented midribs, 

 48 per cent soft tissue, 8 per cent veins (other than the ribs), and 11 per cent 

 the grain. It is noted, however, that these results are only approximate. On 

 analysis the grain bodies were found to have the following percentage compo- 

 sition : Moisture, 8.06 ; pure ash, 40.26 ; potassium oxid, 3.42 ; calcium oxid, 

 26.34; magnesium oxid, 3.13; oxalic acid, 0.82; citric acid, 22.38; and malic 

 acid, 13.58. Analyses of the leaf web, large vein excluding midrib, and small 

 vein are also submitted. The analytical data indicate that the grain is com- 

 posed chiefly of calcium with a small amount of magnesium and potassium in 

 combination with citric and malic acids rather than with oxalic acid. Normal 

 calcium malate was identified by petrographic methods. 



The grain was found not to be responsible for the marked hygroscopic prop- 

 erties of the tobacco, since the amount of water absorbed by it from a moist 

 atmosphere was less than that absorbed by the other kinds of material. The 

 small veins of the leaf showed the greatest hygroscopicity. 



" The grain bodies of tobacco are developed in the course of post-mortem 

 changes which take place during the process of curing and continue during 

 fermentation. A microscopically visible change consists of a more or less com- 

 plete aggregation of the grain-forming substance of all the cells into certain 

 groups of cells. The factors determining the location of these groups are 

 unknown. 



" In the tobacco studied a correlation was found between the grain and 

 burning properties. It is believed that the substances contained in the grain 

 bodies are injurious to the burn, and that the quality of the latter is dependent 

 upon the degree to which the former are aggregated into definite bodies suffi- 

 ciently separated, one from the other, to permit a considerable fire-carrying 

 zone of cells, emptied of grain material, around each. The influence of the 

 degree of aggregation of the grain substance upon the color, texture, and elas- 

 ticity of the leaf has not yet been thoroughly investigated." 



Tabulated and graphical analytical data relative to the burning quality of 

 the tobacco grown on plats to which various kinds and amounts of fertilizers 

 were applied are submitted. 



The chemical composition of lime-sulphur animal dips, R. M. Chapin 

 {U. 8. Dept. Agr. Bui. 451 {1916), pp. 16). — A number of lime-sulphur solutions 

 have been analyzed by the methods previously described by the author (E. S. K., 



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