Water-Content of Plants 41 



plant in the soil, but of chief interest must be regarded the 

 relations of the root-system to the water and the nutrient 

 salts of the substratum. 



From a casual examination of plants in the field it is 

 difficult to form a proper conception of the extent of the 

 root-system. Pull up a wheat plant or any fibrous rooted 

 grass, and the root-system may seem extensive. Proceed 

 in the same manner with a beet or with an herbaceous 

 plant like the sunflower. The root-systems which come 

 to view in these two cases would give an entirely erroneous 

 impression of the relative or actual extent of the roots. 

 A large proportion of roots and rootlets remain in the soil, 

 especially in the case of the fleshy plant. 



Upon a careful examination it is noted invariably that 

 accompanying vigorous growth in the soil there is a sur- 

 prisingly extensive system of small rootlets, and these are 

 usually disregarded in rough estimates of root extent. The 

 only methods of determining approximately the root devel- 

 opment is either by excavating carefully, and then washing 

 away the soil while the roots are in some way effectively 

 supported, or by growing the plants in special root cham- 

 bers. 



29. The rooting habits of crops. - - Plants vary greatly 

 with respect to the distribution of roots in the soil. In the 

 same habitat, or under the same cultural conditions, one 

 plant may show the greater extent of its roots close to the 

 surface, while another may branch more freely at greater 

 depth. Freidenfeld has made a careful study of root- 

 habit in a variety of common plants. 



A study of this distribution of roots under diverse con- 

 ditions is a matter of considerable importance. Upon it 



