60 COLLEGE BOTANY 



with the soil but which cling to trees or other objects and derive 

 their nourishment from the air. They are ver;^' abundant in the 

 moist tropics and have coverings of cells which are especially 

 adapted for the absorption of water from the air. (d) Roots of 

 parasitic plants, which penetrate other plants and feed tipon 



Fig. 37. — Sweet potato showing both fibrous and fleshy roots. 



their juices. The mistletoe and dodder (Fig. -±0) are excellent 

 examples. Plants with roots of this kind are sometimes very 

 injurious to the plants on which they grow, (e) Water roots are 

 formed on many floating plants, such as the duckweed. Willows 

 sometimes produce a specialized root system, which spreads out 

 in the water. The stems of many plants which grow normally 

 in the soil will produce roots if submerged in water or wet sand. 

 The roots of most plants do not produce buds, and this is one 

 of the distinctive characters between roots and stems, but some 



