THE DICOTYLEDONES 



1709 



flowers emit the smell of decomposing flesh and are therefore visited by 

 carrion-feeding flies who are said to efl^ect pollination. 



Fig. 1578. — Rafflesia arnohii. Female flower in vertical section, showing the numerous 

 ovuliferous cavities in the inferior ovary. These cavities are not normal carpellary 

 loculi but are said to originate as intercellular spaces. (From R. Broun, "Miscellaneous 

 Botanical Works".) 



The third interesting family is the Hydnoraceae which are also 

 parasitic in the roots of various trees and shrubs. There are only two 

 genera, Hydnora which is found in Africa, and Prosopanche with one 

 species found on the Pampas of the Argentine (Fig. 1580). The vegetative 

 tissue consists of a branched, creeping, cylindrical or angular rhizome, 

 which grows out from points of attachment on the roots of the host plant, 

 which is often a species of Acacia or Euphorbia. The flowers (Fig. 1581) 

 are elongated, solitary organs, which arise directly from the rhizome. 

 They each consist of three or four thick, fleshy perianth leaves, which are 

 united below and incurved above. The stamens are equal in number to 

 the perianth segments, to which they are attached, and form a ring, on the 

 upper side of which is a large number of pollen sacs. The ovary is inferior 



