IV. The root-system of plants and their role in the 

 water regime of the soil. 



It was stated above that the root-system of plants has an impor- 

 tant significence in the water regime of the soil. 



But first I shall deal briefly with the root-system of various plants, 

 for without a knowledge of their dimensions and the distribution of small 

 roots it is difficult to explain the water processes in the soil ••). 



. The roots of plants develope very rapidly after the germination of 

 the seed, and already in 7 to 10 days time after the appearance of the 

 sprouts they reach 35 to 40 cm. in our cereals, going far beyond the 

 limit of the average ploughed depth. At the beginning of the bushing 

 period the roots of spring cereals attain a depth of 50 cm. (fig. 2) and 

 towards the commencement of flowering the developement of the root- 

 system finishes, or the growth of the roots after that to the attainment 

 of maturity is insignificant. In the case of winter crops, a certain growth 

 of the roots goes on in the interval between the period of flowering and 

 the period of maturity (fig. 2). 



This peculiarity the cessation of the root growth after flowering — 

 distinguishes cereal plants from flowers and dictoyledons, whose roots con- 

 tinue to grow after flowering. 



Then cereals have a second peculiarity. They have always three 

 or more main roots (fig. 3) from which lateral roots branch off whilst 

 dicotyledons have always one main root (fig. 4). Then the main root of 

 cereals leave the root-head in a lateral direction, almost at right angles 

 one to another, forming a polyhedrous pyramid; whilst the main root of 

 dicotyledons grows vertically. 



The limit to which the roots spread downward and sideways (the 

 dimensions of the root system of various plants their length and lateral 

 spread is seen on table IV") is very large towards the end of the vege- 

 tating period. — Spring cereals (fig. 5) reach' a depth of 110 c m. and 



*) A more detailed account of root-systems is included in my work „The 

 root-systems of plants of one years growt". 



