340 



STRUCTURE AND LIFE HISTORIES 



of one flowering plant on another (Fig. 246). In some of 

 these cases as, for example, the dodder (Cuscuta), the para- 

 site may have completely lost the power of elaborating 

 chlorophyll, and thus lack the function of photosynthesis; 



FIG. 248. Dodder (Cuscuta sp.\ in flower. Parasitic on a golden rod 

 {Solidago ulmifolia). (Photo by Elsie M. Kittredge.) 



the parasitism is then complete (Figs. 247, 248 and 249). 

 In other cases the parasite may retain its chlorophyll- 

 apparatus, and hence be only partly dependent upon 

 the host, as in the case of the mistletoe (Fig. 250). 

 Such plants are semi-parasites. Another example of 



