— 30 — 



the soil was denuded of all lis reserve oj water in the root-inliahitahle 

 layer. 



There were also other cases analogous to the above (see fig. 11. 12, 13). 

 The downward movement of the water (fig. 11) did not cease from 

 October to april, because the soil was not frozen up during winter dee- 

 per than 40 cm., and water confined to percolate into the layers deeper 

 than 40 cm. up to april. But by that month the roots of the barley sown 

 on the 25-th of february 1906, had already penetrated to such a depth 

 that they took up even the lowest horizon of the humid layer and the 

 percolation of water into deeper layers ceased by the end of June; r/;7r/ <-// 

 the period of reaping all the reserve water in the root layer was expeuded. 



In the next instance (fig. 12) we have to deal with wild instead of 

 cultivated plants - intermediate (June) green fallow in 1905. Here also the 

 accumulation of water, or, which is the same thing, the thickness of the 

 humid layer commenced in the previous autumn of 1904. During win- 

 ter the condition of the humid layer remained unchanged owing to the 

 whole layer freezing up and the water becoming solid and immovable. 

 Although the lowest horizon of the humid layer reached a depth of 100 

 cm. in may 1906 (fig. 11) and only reached 45 cm. in april 1905, 

 nevertheless, in both cases, no surplus of serviceable water remained, at 

 the begining of July. In both cases (fig. 11 and 12) the water was consu- 

 med by cultivated and wild plants. It is evident therefore that as regards 

 the consumption of water there is no difference between wild and culti- 

 vated plants. By midsummer all the reserve of serviceable water in the 

 root layer is utterly exhausted. 



It is not only spring growths that entirely consume the whole of the 

 useful water by the end of the period of vegetation. The same is observed 

 in the case of winter growths. In iig. 13 the state of humidity is depic- 

 ted on fields sown with winter wheat following a crop of barley (rota- 

 tive culture) and after black fallow (fig. 14). In both of these cases the 

 reserve water in the root layer is expended by reaping time. 



Maize (f'g. 15) impoverishes the reserve useful water somewhat la- 

 ter that grasses — not before august. 



Potatoes (fig. 16) and flaxx stand out quite separately from all cul- 

 tivated annuals at least from those investigated by me. As short-rooted 

 plants, they do not require a deep layer, and from 1 to 2"/o ol useful water 

 remains in the soil after their maturity in august. 



On diagram 17 the yearly course of humdity in the soil of waste 

 land in shown as observed from year to year. Usually the humid layer 

 here, in spring, is not thicker that 40 or 50 cm. and often about 30 

 cm. Towards midsummer it gives up all its useful water to the roots the- 

 rein and then remains dry until autumn. But what is particularly inte- 



