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INTRODUCTION TO PLANT GEOGRAPHY 



[chap. 



whose crown has meanwhile become large and heavy, as a hollow 

 but independent tree in its place (Fig. 149). Species of Cltisia, 

 forming large crowns but seldom killing their hosts, are often the 

 most plentiful stranglers in the South American rain forest. 



6. Saprophytes. These, the plants obtaining their nutriment from 



Fic. 149. — An old specimen of Strangling Pig in which the roots serve as trunks, 

 the original ' host ' having disappeared. 



dead organic matter, together with the parasites, comprise the non- 

 green, heterotrophic components of the tropical rain-forest vegeta- 

 tion. As in temperate woodlands, the vast majority are Fungi and 

 Bacteria which aid in organic breakdown — chiefly near the surface 

 of the soil. There are, however, in addition usually some small 

 associated flowering plants such as certain Orchids and mem- 

 bers of the Burmannia family (Burmanniaceae) and the Gentian 

 family (Gentianaceae), as well as others of the Triuridaceae and 

 Balanophoraceae, which contain little or no chlorophyll and live 

 by the same saprophytic means. They are chiefly found in deep 

 shade on areas of the forest floor where dead leaves tend to accumulate 



