October 13, 1905.] 



SCIENCE. 



461 



ness and temperature up to the time of 

 harvest. The wheats grown under the 

 opposite conditions of a winter rainfall and 

 a dry summer, as on the Pacific slope of 

 North America, or an evenly distributed 

 rainfall as in England or France, are on 

 the whole weak. The differences in this 

 quality are considerable when measured 

 commercially ; for example, in most seasons 

 the best Manitoban wheat will be worth 

 20 to 25 per cent, more than a correspond- 

 ing grade of English wheat on the London 

 market. The source of strength lies among 

 the nitrogenous constituents of the wheat 

 flour ; it can be measured roughly either by 

 determining the proportion of nitrogen in 

 the flour, or by the old process of washing 

 away the starch and leaving the gluten. 

 Neither process agrees exactly with baking 

 tests, nor do any of the more recent at- 

 temps to differentiate the wheat proteids 

 by their solubility in various media, as, for 

 example, the determination of the so-called 

 gliadin glutenin ratio. In fact, in the 

 present state of our knowledge of the possi- 

 bilities of identifying and separating the 

 proteids in a pure state, there is little like- 

 lihood of being able to make out the subtle 

 differences of chemical composition which 

 result in the varying quality of the wheat 

 proteid mass. For example, the relative 

 strength of different varieties of wheat 

 grown under similar conditions will follow 

 the order in which the wheats are placed 

 by their content in nitrogen; yet if, as at 

 Eothamsted, an increased nitrogen content 

 in the wheat is brought about by excessive 

 nitrogenous manuring, the product is ac- 

 tually considerably weaker than wheat on 

 the other plots grown under more normal 

 conditions. The manuring, while increas- 

 ing the nitrogenous matter of the wheat, 

 has probably introduced a new factor in 

 the shape of a more prolonged development 

 resulting in the lack of those final changes 

 in the nature of the wheat proteids which 



make for strength. This seems to be indi- 

 cated by the fact that on storage this par- 

 ticular abnormal wheat gradually increases 

 in strength up to the normal, though never 

 to the degree that would be indicated by its 

 nitrogen content. But though the chem- 

 ical methods of estimating the strength of 

 wheat have as yet proved inconclusive, 

 some idea of the factors determining this 

 quality has been reached from practical 

 baking tests combined with measurements 

 of the gluten and nitrogen content of the 

 flour. In the first place manuring proves 

 a very small factor ; the composition of the 

 grain of wheat is extraordinarily stable 

 and the plant reacts to diversities in nutri- 

 tion by producing more or less grain rather 

 than by altering its composition. Even 

 under the exceptionally pronounced varia- 

 tions in the manurial conditions of the 

 Rothamsted plots, the composition of the 

 grain fluctuates more with changing sea- 

 sons than with changed manuring. Within 

 the limits of healthy growth and ripening 

 the date of sowing the wheat has no effect 

 upon the quality of the grain; the same 

 wheat sown at monthly intervals from Oc- 

 tober to March gave practically identical 

 quality in the grain, and a number of com- 

 parisons between autumn and spring sow- 

 ing led to no definite conclusion. Soil has 

 also a comparatively small effect, though, 

 of course, different soils, by inducing dif- 

 ferences in the supply of water to the 

 plants and in the temperature, practically 

 result in differences of climate. The effect 

 of climate is large, whether tested by grow- 

 ing the same variety in different countries 

 or by inducing artificial variations in the 

 climate of wheats grown under experi- 

 mental conditions. But while the climatic 

 factor proves to be large it is less than was 

 anticipated ; an English soft wheat, for ex- 

 ample, grown on the Hungarian plain for 

 two seasons, has not altered greatly in char- 

 acter nor taken on the characteristic ap- 



