OTHER METHODS OF OBTAINING FOOD 213 



is benefited by drawing its own nutriment from the cells of 

 the root into which it has penetrated. The fungoid mantle 

 is known as a myco- 



ft 



rhiza ; it is present 

 not only on the roots 

 of the Cupuliferae, but 

 on those of Poplars, 

 and many Heaths and 

 Rhododendrons. 



A curious case of 

 this kind of relation- 

 ship is shown by 

 Monotropa, a member 

 of the Heath family 

 which possesses no 



* FIG. 102. A, EPIPHYTIC MYCOBHIZA OF Fagus 



Chlorophyll. Mono- sylvatica (x 2); B, TIP OF BOOT PABTIALLY 



DENUDED OF THE INVESTING MANTLE ( X 30). 



tropa possesses a (After Pfeffer.) 



rhizome, from which 



rise sub-aerial stems from ten to twenty centimetres high, 

 bearing succulent membranous leaves. From the rhizome 

 are given off crowded masses of roots which are covered 

 with a mycorhizal mycelium, arid are embedded in humus. 

 There being no chlorophyll apparatus, Monotropa is de- 

 pendent entirely on the mycorhiza for its nourishment. 

 The latter is entirely saprophytic. We have here a curious 

 case of the complete dependence of a higher plant upon a 

 more lowly one. 



A complete symbiosis between two green plants is 

 occasionally met with. A good instance is afforded by the 

 Mistletoe and the plants upon which it grows, usually 

 either the Poplar, the Silver Fir, or the Apple-tree. The 

 seed of the Mistletoe is left by a bird upon a branch of 

 one of these trees, and under appropriate conditions it 

 germinates. The root of the seedling penetrates into the 

 bark of the tree and grows inwards till it reaches the wood. 

 It makes its way no further, but maintains its position 

 there, and as the branch gradually thickens by the activity 



