1258 AGRICUIyTURAX BOTANY, CHEMISTRY AND PHYSIOI^OGY OF PI,ANTS 



In 1913 it was noticed for the first time in the laboratory that in " Bie- 

 lotourka " wheat cropped from the same pot some grains were found with 

 glassy fracture and others with floury fracture, and that the number of floury 

 grains was greater in the pots with greatest soil humidity. 



In 1914 and 1915 experiments were carried out in order to study the 

 distribution of the floury grains in the ear, as it was at first assumed that 

 the presence of these grains in the wheat ear of " Bielotourka " was a de- 

 fect which must have occurred in the grains of the upper part of the ear, the 

 said grains being incompletely ripe or developing under abnormal condi- 

 tions. The result of the experiments carried out with great care was how- 

 ever negative, that is to sa3^ it was not possible to detect any relation be- 

 tween the location of the grain on the ear and the character of its fracture. 



In 1915 experiments with pure lines of " Bielotourka " were made, the 

 humidity of the soil in the pots being maintained at 50, 60, 70, 80 and 90 % of 

 complete saturation, or approximately at 20, 24, 28, 32 and 36 % of its 

 weight when completely dry. The experiments demonstrated that while 

 with 20 % of moisture in the soil all grains have a glassy fracture, with an 

 increase above this percentage the grains with more or less clear floury 

 fracture appear, and in the pot with 35 % of moisture in the soil the grains 

 with glassy fracture form only 10.8 % of the total crop. Thus the glassi- 

 ness or floury fracture of the grain of "Bielotourka " wheat, even within 

 the limits of a pure line, does not represent a constant character, but the 

 fracture ma}^ be modified under the influence of external factors intervening 

 in the course of growth, and, in the particular case under study, under the 

 influence of the degree of moisture of the soil. 



In order to investigate the influence of osmotic pressure on the charac- 

 ter of the " Bielotourka " grain, experiments were made in the greenhouses ; 

 effect of changes in the osmotic pressure were studied by adding to the soil 

 the necessary quantity of the following salts : chloride, sulphate and nitrate 

 of sodium, ammonium sulphate, ammonium nitrate. The appended table 

 brings out clearly the relation between the osmotic pressure (determined 

 in this particular case by the addition of sulphate of soda), and the nature 

 of the grain of " Bielotourka ". 



Evidently therefore the quantity of grains with glassy fracture in- 

 creases with the rise of the osmotic pressure in the soil moisture, and at the 

 pressure of 7 atmospheres all grains had become glass}'. 



It follows from a comparison of the data relating to the other salts 

 experimented on, that their action is not equal ; nevertheless, by gradually 

 increasing the osmotic pressure of the soil solution a greater quantity of 

 glassy grains is obtained, and at a given pressure for each salt, all the grains 

 become glas.sy. Thus by modifying the pressure of the salt salution it is 

 possible to obtain glassy or floury grains at will with " Bielotourka " wheat. 

 The following fact was also clearly brought out : sodium salts exert a differ- 

 ent action of the formation of the glassy grain, according to their acid radi- 

 cles. Sulphate of sodium exerts the feeblest action ; chlorine acts more and 

 nitrate of soda still more strongly ; with the addition of this last salt in a 

 sufiicient quantity to raise the osmotic pressure to 2 atmospheres, almost 



