SCIENCE IN WHEAT-GROWING. loi 



SCIENCE IN WHEAT-GROWING. 



By M. p. p. DEHfiEAIN. 



THE chlorophyll cells and the leaves of the plant may be re- 

 garded as little laboratories elaborating vegetable matter; 

 they work upon the carbonic acid, which the enormous quantity of 

 water they contain enables them to extract from the atmosphere, 

 reduce it, and form with the residue from its decomposition, 

 after the elimination of oxygen, sugars and cellulose, straw- 

 gum, vasculose, and all the ternary matters composed of carbon, 

 oxygen, and hydrogen ; these cells likewise reduce the nitrates 

 which are brought to them at the same time with phosphoric 

 acid, potash, and silica, by the water which constantly traverses 

 the plant, entering it at the root and being exhaled from the 

 leaves. 



If rain is frequent and the soil well moistened, the cells will 

 continue their work for a long time; they will elaborate much 

 vegetable matter, and the plant will grow. But the course is not 

 the same if rain is scarce and the soil is parsimonious in provid- 

 ing for the enormous expenditure of water which the wheat makes. 

 I have found that a leaf of wheat exhales, under one hour of inso- 

 lation, a weight of water equal to its own. When the earth, in- 

 sufficiently watered by rain, becomes incapable of supplying this 

 jjrodigious consumption, desiccation of the organs is produced, 

 and it is always the oldest leaves which dry up and perish first. 

 A May rarely passes without one seeing the little leaves fixed at 

 the base of the stem soft, flabby, and withered. If we submit 

 them to analysis, we find that they have let escape some nitrogen- 

 ized matter, phosphoric acid, and potash, which they contained 

 while they were living, green, and turgescent. It is well to lay 

 stress upon this death of the leaves, and on the departure of the 

 materials they contain ; when the leaf dies, one of the small ag- 

 glomerations of working cells is closed, the quantity of matter 

 elaborated is then less than if it had continued its task, and as the 

 closure of these little laboratories is determined by their desicca- 

 tion, we conclude that the quantity of vegetable matter formed 

 during dry years is limited, and that the stems are shortened and 

 there is little straw. 



At the moment when desiccation begins the nitrogenized mat- 

 ter which forms the protoplasm, the living part of the cell, is 

 metamorphosed, and takes an itinerant property that permits it to 

 pass through the membranes and migrate toward the new leaves, 

 carrying with it its usual accompaniment of phosphoric acid and 

 potash. This transportation of some of the elaborated material 

 from the lower leaves toward the upper leaves goes on through 



