OF THE \ 



UNIVERSITY, J 



ROOTS: ROOT SYSTE. 



of root systems, and these are seen to be peculiar to certain plants. 

 For example : 



45. The tap-root system. Plants possessing a tap-root 

 system are those which have a prominent root called the tap 

 root, which is stout and extends downward to some depth in the 

 soil, as in the dandelion. This is usually developed from . the 

 primary root. There are numerous lateral roots but they are 

 usually slender. The carrot, parsnip, etc., are other examples. 

 The fibrous-root system is very different. The roots are com- 

 paratively slender- and much branched, as in the bean, corn, 

 etc. Fascicled roots. Thickened or fleshy roots developed in 

 clusters or fascicles are called fascicled roots. A good example is 

 seen in the dahlia with a tuft of stout fusiform roots. 



Fig. 32. 

 Fascicled roots of the dahlia. 



46. Relation of root system to the soil. The relation of 

 the root system of plants to the soil is a very important one, and 

 is governed to some extent by the nature of the soil, the moisture 

 content and distribution of the plant food. Plants with a tap- 

 root system have an advantage over those with a shallow fibrous- 

 root system in dry soils or in dry weather, since the roots are able 

 to reach the moisture at the lower levels in the soil. Evaporation 

 removes the moisture from the surface layers rapidly in dry 

 soil and in dry periods, and plants with a root system developed 

 near the surface are the first to suffer. Hickory and walnut 

 trees have a tap root which extends to great depths in the soil, 



