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BIOLOGY: GENERAL AND MEDICAL 



Upon the roots of the Cycas, or sago palm, certain species 

 of Anabsena are always symbiotic and perhaps parasitic. 

 Higher plants may also adopt the parasitic life. The 

 "dodders," so often found upon meadow plants, are 

 typical parasites. From a seed that falls upon the ground 

 a delicate filament makes its appearance climbing like 

 a vine about the stems of some other plant. Soon deli- 

 cate rootlets grow into the tissues of the host, and the 



FIG. 109. The European mistletoe (Viscum album). (Kerner and Oliver.) 



primitive root of the parasite dies. As it now derives 

 its entire sustenance through the rootlets that have 

 penetrated the plant to which it clings, it can dispense 

 with organs of its own and has neither terrestrial roots 

 nor leaves. It grows rapidly, forming a pale colored 

 tangled filamentous mass that bears abundant small 

 flowers in clusters, and produces small seeds. 



Other striking examples are the mistletoes. These 

 plants, of which hundreds of species are known, produce 



