AERIAL ROOTS 23 



fleshy roots for the inimediate production of new plants or 

 slips. Sometimes, new plants are also produced directly from 

 fibrous roots, as in the case of the poplar, plum, etc., but as 

 a rule new plants are not produced from the roots. 



Length of Life.- Plants which live but one year, as in the 

 case of the radish are known as annuals; those that live for tw^o 



Fig. 13. — Corn plants sliowing the aerial roots. 



years, as in the case of the turnip, are known as biennials; while 

 those that normally live for several years, as in the case of 

 trees, are known as perennials. 



Aerial Roots. — Eoots are frequently borne on parts of the 

 stem above the ground, and are known as aerial roots. (Fig. 

 13.) These roots tend to reach the soil and serve as prop roots 

 and help to support the plant against wind storms. They are 

 well developed on the lower part of the corn, and are especially 

 prominent on those plants which have not been tilled properly. 



