32 GROWTH AND WORK OF PLANTS 



character of the branching. There are several types of root 

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

 For example: 



52. 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 

 of tap roots. The fibrous-root system is very different The 

 roots are comparatively 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 

 (spindle-shaped) roots. 



Fig. 35- 

 Fascicled roots of the dahlia. 



53. 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 goverened 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. Evapo- 

 ration removes the moisture from the surface layers rapidly in dry 

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



