16 EXPERIMENT STATION RECORD. 



composition of cereals and jjotatoes diirinj;- dry and wet years. Accord- 

 ing to Delieraiii the spikes of oats contained 12.37 per cent of nitrogen 

 in 1879, a dry year, and only (>.;")(> ])er cent in 1878, a very wet year, the 

 conditions being otherwise the same. 



In comparative experiments with tobacco, Mayer ' studied the influ- 

 ence of water upon the production of nicotin, and found that the more 

 moist the soil the less the nicotin. The percentages of nicotin in dry 

 matter of tobacco grown on 3 soils containing ditt'erent amounts of 

 water were as follows: In the first, 2.7 to 3.1 per cent; in the second, 

 1.45 to 1.75, and in the third, 1.05 to 1.02. The total dry matter varied 

 with the nicotin content, but not proportionately. This indicates 

 that without injuriously affecting the growth of the plant the formation 

 of nicotin may be greatly reduced. In the tubers of artichokes the 

 content of potash and phosphoric acid is greater in moist than in dry 

 years.2 In a dry year the leaves are rich in phosphoric acid, the amount 

 in the tubers being proportionately small. 



For each i)eriod of growth of an organ of a plant, therefore, there is 

 a certain definite portion of internal water necessary for normal and 

 healthy condition, the same being true for each stage of develoi^ment 

 of the entire plant. Water produces in the organ or plant under con- 

 sideration a state of turgescence and normal hydration. This turges 

 cence is produced in each vegetative stage by variable proportions of 

 water, as has been shown by the author's investigations as well as those 

 of Gelesnotf,^ Sorauer,^ and Jumelle.^ The study of the variation in 

 the water content of plants is necessary, therefore, in order to determine 

 how water may be most economically and advantageously distributed 

 by means of irrigation. From the results of his experiments the 

 author has been able to draw curves for the development, respectively, 

 of the hypocotyle, cotyledons, root, stem, and leaves. He has also 

 studied the development in general of the entiie plant. These curves 

 are based on the proi)ortion between dry weight and total weight of 

 each organ at different periods of growth, noting also the duration 

 of the different stages of growth. 



The root usually presents a weakened condition at the flowering 

 period, at which time there is a transfer of substances toward the 

 flowers. This weakening remains for a considerable time and is espe- 

 cially marked if the plant is ui)on a very dry soil. If, after flowering, 

 the root is furnished with an increased supply of moisture, the period 

 of growth is stimulated and j)roh)uged. When the root prematurely 

 dries, the vitality of the entire plant is soon checked. 



Eoots play a role in regulating the water content of the aerial part. 

 If the quantity of dry weight tends to become too great, the root 



' Laadw. Vers. Stat., 38, p. 453. 



2Anii. Agron., Feb., 1892. 



3 Quantito et repartition de I'eau dans lea organes des plantes, 1876. 



•» Influence de I'abondance ou dn manque d'eau, Bot. Ztg., 1878, p. 14. 



^Sur le d^veloppement des plantes anuuelles, Rev, g^n. Bot., 1889. 



