40 DKSCUIPTIVK UOTANY. PART I. 



forming roots : this is often the case with the white 

 poplar, and certain elms which throw up their nu- 

 merous suckers, to the great detriment of the pasturage 

 when planted in meadow land. 



Besides the important purpose which the root is more 

 especially destined to serve, of absorhing nutriment, it 

 is generally so placed as to take firm hold in the ground, 

 and thus enables the plant to maintain its position in 

 one and the same spot during its lifetime. There 

 are, however, certain plants, as the common duck- 

 wi-i'ds (Lemrun, fig.'l\. b), which float on the surface 

 of ponds, whose roots are suspended in the water 

 without ever reaching the bottom. There are others 

 termed " air-plants" (some of the Orchidece), whose 

 roots cling closely to the branches of trees, and derive 

 their nutriment from the moist atmosphere perpetually 

 hanging over a tropical forest ; and these plants could 

 not live long if they were planted in the ground. 



(40.) Forms of Roots. The various forms which 

 roots assume need not be dwelt upon here ; they are 

 such as may be readily learnt in any elementary work, 

 but their description would involve us in details for 

 which we have not space. 



(41.) Appendages to ttie Root. There are not many 

 distinct appendages to be found on roots. In some 

 fibrils, there are swollen nodosities (fig. 29-)> an d on 



others there are little tuberous excrescences. In 

 some, the fibrils become very fleshy, and are swollen 

 into masses ( fi<j. 30.), having an ovate (), palmate 



