ROOTS 



15 



,plerO),-Ti. 



endodermis 



perl6/em 

 Aerwaloqen 



system of rootlets developed. Corn is found to have a large 

 part of its lateral root system in the surface layers when the 

 soil is poor. The general form of a root system may be 

 changed by transplanting. As a result of the necessary in- 

 jury accompanying this process, there is developed a compact 

 root system. Desert plants usually have an extensive root 

 system, reaching to considerable depths, Swamp plants, 

 even trees, develop a spreading, and comparatively shallow 

 root system. The method and amount of watering affect 

 the general shape of the 

 root system. Fruit trees, 

 for example, send their 

 roots into the deeper soil 

 layers if the surface layers 

 are dry, but if the ground 

 water level is close to the 

 soil surface the root sys- 

 tem will be more super- 

 ficial. The character of 

 the root system is often 

 an index of soil conditions. 

 General Characteristics 

 of Roots. — It will be re- 

 called that the seed plant 

 body possesses a number 

 of members, each with 

 more or less distinctive 

 characters. . Roots have characteristics which stand out 

 in quite marked contrast to those of other plant members. 

 Roots do not give off their branches in a regular order, 

 as stems do. They do not bear buds, except in very rare 

 cases. Roots usually bear a root cap (Fig. 5) which pro- 

 tects the growing point, while the growing point in stems 



region of ^ 



ariatesir 

 iellmu/tif^ica 



Fig. 5. — Median lengthwise section of 

 the apex of a root of barley. (After 

 Slrasburger.) 



