BOTANY. 105 



Besides these varieties of roots, there are several others 

 which are peculiar, and distinguished by not being necessa- 

 rily fixed in the soil. 



Aerial roots are those which grow from some part of the 

 plant above the surface of the soil in the open air. Some 

 creeping plants, as the ground ivy, send forth these roots from 

 their joints. The screw-pine also sends off roots which are 

 several feet in length before they reach the ground. Such 

 roots are often seen in the common maize. 



Floating roots belong to plants which float upon the surface 

 of water. The water-starwort is said to float upon the surface 

 until flowering, when it sinks and takes root in the mud till its 

 seeds ripen. 



The epiphytes, or plants fixed upon the branches of other 

 species, derive their nourishment mostly from the air: such 

 are some species of moss. 



Parasites are those plants which grow upon other plants ; 

 and some of whose roots are said to penetrate their tissues 

 and subsist upon their juices; while the roots of others are 

 aerial, and derive their food from the air : such are the mistle- 

 toe and dodder. 



Roots are divided again into three varieties, viz: annual, 

 biennial and perennial, according to their duration. 



Annual roots are those which live only one year, and must 

 be raised from the seed, sown every spring, as beans, peas 

 and cucumbers. 



Biennial roote_are those which live two years and do not 

 blossom the first season, but they produce flowers, fruit and 

 seeds the second year, and then die : such are the beet, cab- 

 bage and carrot. 



Perennial roots live several years, some of them, as forest 

 trees, live to a very great age: the grasses, dandelion and 

 asparagus are other examples. 



