THE BOOTS 29 



securely in place. Here the original function of fixa- 

 tion alone is carried on, since generally no opportu- 

 nity is offered to absorb food. So finely are these 

 roots adapted for anchorage in difficult places that 

 they can secure a foothold on the polished surface of 

 a marble column or a sheet of glass. This may be 

 seen in the ivy of the gardeners {Ficus). 



29. Stilt 7Vots. — A special adaptation of the 

 fixative function is to be seen in the roots which 

 start from the stem a short distance above the 

 ground and extend outwardly and downwardly until 

 they enter the soil several inches perhaps from the 

 main stem. Such roots brace the stem, and if the 

 tips form branches after entering the soil, their effi- 

 ciency is still further increased. This may be seen 

 in the wheat, corn, and other grasses, as well as in 

 the palms and the mangroves. Go into a cornfield 

 in early autumn and note the stilt roots. Pull a 

 stalk sidewise and note their action. 



30. Columnar 7^oots. — In many of the forest 

 trees, such as the beech, large roots are formed at 

 the surface which take the form of an upright thick 

 sheet of wood tapering in width toward the outer 

 end where it is covered by the soil. These also 



