— 25 - 



spread out to almost the same extent. Maize is an exception, for its root- 

 system is greater in width (up to 150 cm.) than in length. The root 

 system of winter cereals is longer than that of spring cereals and reaches 

 130 c. m. (rye). Then in wheat it is flatter from top to bottom, and in 

 rye it is stretched lengthways, Amongst dicotyledons, sunflowers and 

 beetroots haee very long root-systems (over 4h'-> feet): others like flax, 

 cress, poppies, peas (fig. 7), beans (fig. 8) and cotton have very short- 

 ones (about 100 cm.); potatoes (fig. 9) very short (about 60 cm.) 



Cereals (fig. 5) have a much denser root network than dicotyledons 

 (fig: 4 and 7) which have a comparatively weakly developed root-system, 

 especially flax with small roots of the 2-d, 3-d and lower orders. It must 

 be noted here that t/ic thickness of the root network is almost equal thro- 

 ughout the soil layer which they occupy. But small roots are always 

 deuser in that layer which holds the most moisture whether it be the 

 upper, intermedeate or lower part of the root-inhabited layer (fig. 6). 



Perennials like green fodder, shrubs and trees extend their roots 

 several fathoms deep, sometimes over 10; green fodder, like lucerne, 

 send their central root down to 8 even 10 fathoms; laterally the side 

 roots do not extend beyond 60 or 80 cm. The side roots of trees extend 

 from the central one to 5 or 6 fathoms, the white acacia (Robinia pseu- 

 dacacia) even to ten fathoms. 



These morphological properties of the roots of our field plants must 

 be kept in view in order to understand the role played by them in the 

 distribution of water; for the principal, almost the only factor in that 

 distribution, is the root-system (as regards soil layers deeper than 50 cm. 

 at any rate). The denser the root network of a plant, the easier it will 

 be for that plant to find water of course. But plants with a weakly deve- 

 loped root-system, like flax and cress, must have at their disposal a 

 plentiful supply of water. This apparently explaius the preponderating 

 culture and independent growth of grasses on dry steppe areas, for their 

 denser root network can abtain the requisite quantity of water with gre- 

 ater facility. 



The data worked out by me last year concerning the depth pene- 

 trated by the root-system of various plants of not less than 110 cm. 

 (31;'l> feet) for certain others much deeper — indicates that in order to ob- 

 tain an abundant harvest the root-inhabited layer of soil should be moist 

 throughout and should hold a sufficient quantity of useful water; that is 

 of water which the plants can benefit by. It must not be forgotten that a 

 certain quantity of water is contained in various soils which roots cannot 

 make use of. The finer the soil, the more useless water it contains, and 

 in certain types of soil it exceeds lO^/o. 



