THE ROOT 



of the turnip napifortn. The root of the radish is spoken of as 

 fusiform. 



In some instances the primary root is soon rivalled in size by 

 its branches ; it may even cease growth altogether. Such plants, 

 on being pulled out of the ground, exhibit a bunch of slender 

 roots, the chief of which are all much the same diameter and 

 length ; roots of this character are described as fibrous, and are 

 well exemplified in common groundsel and grasses. 



5. Adventitious Roots.— The roots of monocotyledonous 

 plants differ in their development from those of dicoty- 

 ledons. The single primary root of 

 the onion, for example, lasts but a 

 short time, and is succeeded by others 

 which do not arise as branches upon 

 the primary one, but spring from the 

 very short stem of the plant. Roots 

 which arise on stems and leaves, or on 

 various parts of the roots of plants, 

 but not in acropetal succession are 

 described as adventitious. They are 

 very common upon all monocoty- 

 ledonous plants of the farm and garden, 

 and may be considered the chief 

 ones which such plants possess. In 

 wheat, for example, the embryo within 

 the grain possesses three roots ; in 

 barley, five or six. These are, how- 

 ever, merely temporary structures of 

 Fig. 10.— Young barley plant show- use during the earlier stages of growth. 



ing adventitious roots (a) grow- xi iX. ^- ^ i.\. \. ^ i- i 1 » 



ing out from the first joint or -By the timfe the whcat Or barley plant 



node of the stem. i_ i_ ._ r 1 j r i 1 



has begun to unfold a few leaves above 

 grouna the primary roots of the embryo are succeeded by 

 adventitious roots which grow out from the lower nodes or joints 

 of the stem near the surface of the soil (Fig. lo). 



