320 



ECOLOG Y. 



Mycorhiza. 



603. Many others of the higher plants have fungi associated with their 

 roots. Such roots are mycorhiza. In some genera of the orchids the roots 

 form a compact mass resembling coral growth, as in the coral-root orchid. 

 The curious Indian-pipe (monotropa) has roots which form a large closely 

 branched mass of thickened short roots. In these cases the fungus lives in 



Fig. 423. 

 Dodder. 



the cells of the root and some of the threads of the fungus extend to the 

 outside into the soil, and perhaps partly serve as absorbent organs since the 

 root hairs are very rare or altogether absent on such roots. The Indian- 

 pipe plant possesses no chlorophyll, the fungus in its roots probably assimi- 

 lates carbonaceous food from decaying organic matter in the soil, and gives 

 it up to its host. 



604. Mycorhiza with the fungus in the roots are endotropic mycorhiza. 

 The root tubercles of the legumes also belong to this class. Ectotropic my- 



