ROOTS: KINDS OF ROOTS 



2 9 



which absorbs moisture from the air. Another example common 

 in greenhouses is the wandering Jew (Tradescantia}. The 

 aerial roots grow from the joints, usually two roots from each 

 joint. Good examples of aerial roots can be seen in the case 

 of the climbing poison ivy, English ivy, trumpet creeper, etc. 

 These serve to hold the vine to the tree or other support on which 

 it is climbing. 



49. Bracing roots, or prop roots. In some plants where 

 the fibrous-root system in the soil is not sufficient to support the 

 heavy plant upright, aerial roots 



are developed a short distance 

 above the ground and as they 

 reach the soil serve to prop or 

 brace the plant. Good exam- 

 ples are seen in the Indian corn, 

 and in the screw pine grown so 

 commonly in greenhouses. A 

 classic example of prop roots 

 is seen in the banyan tree of 

 India where numerous roots 

 grow downward from the wide 

 spreading branches. The man- 

 grove along the coast in the subtropical regions of Florida is 

 another example. 



50. Strangling roots. In some tropical countries there are 

 trees (Clusia) which begin their life as seedlings on other trees 

 from seeds which have lodged in the fork of a branch or some 

 other landing place. Slender roots grow down to the ground, one 

 of which forms this part of the trunk. Other roots coil around 

 the foster tree. When the Clusia becomes a large tree these 

 roots wrapped around the foster tree tightly strangle and kill it.* 



51. Fleshy roots, or root tubers. There are roots or por- 

 tions of roots which have become large and fleshy, as in the 

 sweet potato or the dahlia. Such roots are reservoirs where 

 plant food is stored to be used later by the plant for growth or 



* See "A Tragedy of the Forest," Torreya 8, 253-259, 1908. 



Fig. 34- 

 Bracing roots of Indian corn 



