[Chap. XLI 



NON-GREEN PLANTS 



509 



Fig. 224. The evergreen mistletoe is conspicuous on deciduous trees during the 



winter months. 



How frequently this process occurs is unknown. The roots of some plants, 

 such as those of bastard toad flax of the eastern states, and of the desert 

 shrub, Krameria, of the southwestern states, habitually form haustorial 

 unions with the roots of man^' other plants. It is well known that unions 

 occur among the roots of adjoining forest trees. Whether they are of 

 any yalue to the trees is not known. 



Some non-green seed plants, such as the small purple beechdrops at- 

 tached to the roots of beech trees and the slender climbing dodder which 

 becomes attached by haustoria to the stems of a great yariety of hosts, 

 obtain food directly from green plants. The Indian pipe, when casually 

 obseryed, appears to be a saprophyte liying on the litter of decaying 

 leayes on the forest floor, but it apparenth obtains all its food from 

 fungi which digest the fallen leayes, and also liye in and on its roots. 

 Seyeral layers of fungal filaments completely invest each of its many 

 short roots, and numerous branching filaments of the fungus peiTneate 

 the surrounding layer of decayino; leaves and humus. Owino^ to the sur- 

 rounding sheath of fungal filaments, the cells of the roots of Indian pipe 

 are not in direct contact with the soil. 



Fungi that live in such intimate relation with the roots of plants are 



