W. E. Brenciiley and A. D. Hall 215 



whole plant to account for the rise in dry matter, &c. that is observed in 

 the grain and straw during the migration period. The question of 

 when nutrition and assimilation finally cease can only be definitely 

 settled when the roots also can be examined, and experiments to that 

 end arc now in progress. Meantime the evidence derived from our 

 experiments is against the view that either nutrition or assimilation 

 ceases before the final ripening off of the wheat grain ; this, however, 

 may only be true for the comparatively humid English climate where 

 the wheat plant retains some green active tissue until harvest is close 

 at hand. 



Summary. 



A study during 1907 and 1908 of various plots of wheat cut at three- 

 day intervals leads to the following general conclusions : 



(1) The whole plant, and with it the nitrogen, ash, and phosphoric 

 acid it contains, increases in weight until about a week before it would 

 be regarded as ready to cut. Some decrease of dry weight takes place 

 during the last week. 



(2) In the formation of the grain three stages may be distinguished : 



(a) a period during which the pericarp is the most prominent 



feature, 



(b) the main period during which the endosperm is filled, 



(c) the ripening period characterised by the desiccation of the 



grain. 



(3) For the filling of the endosperm each plant possesses as it were 

 a special mould, and continually moves into the grain uniform material 

 cast in that mould, possessing always the same ratio of nitrogenous to 

 non-nitrogenous materials and ash. The character of the mould 

 possessed by each plant is determined by variety, soil, season, &c. 



(4) The main feature of the ripening process is desiccation rather 

 than the setting in of such chemical changes as the conversion of sugars 

 into starch, non-protein into protein, though the latter change also takes 

 place. 



(5) The maximum dry weight of grain is attained a day or two 

 before the grain would be regarded as ripe by the farmer. Allowing for 

 the fact that the tillered shoots are a little behind the central shoots, 

 no loss of weight in the crop will be incurred by cutting before the 

 corn appears quite ripe, while a number of accidental mechanical losses 

 due to birds, shedding, weather, may thus be avoided. Other experi- 

 ments have shown that, though there may be no gain, there will be no 

 loss in the quality of the wheat due to such early cutting. 



