SAPROPHYTISM AND SYMBIOSIS 



339 



reason why it is so difficult to transplant many of the 

 heaths; the delicate adjustment between the plant and 

 the mycorrhizal fungus is disturbed in transplanting, and 

 the soil conditions in the new habitat are not favorable 

 to its reestablishment before the plant dies. 



The Indian-pipe and the false "beech-drops" (Figs. 230 

 and 231), both belonging to the heath family, also pos- 

 sess endotrophic mycorrhizas. 



FIG. 247. Dodder (Cuscuta sp.\ parasitic on geranium (Pelargonium)- 

 A few seedlings at the left are still rooted in the soil, and are not yet at- 

 tached to the host-plant. They eventually sever all relation with the soil. 



311. Parasitism. In some cases of symbiosis, as stated 

 above, only one plant derives any benefit from the union, 

 which may or may not be of positive injury to the other. 

 Such is the case with the endotrophic mycorrhizas, already 

 mentioned. There are many instances of the parasitism 



