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TEXTBOOK OF BOTANY 



Fig. 116. Prop roots of red mangrove (Rhizophora) in Bermuda. Photo by B. E. 

 Dahlgren, Field Museum of Natural History. 



plants but also in some species become the only region of entrance of 

 water and mineral salts. 



Finally, there are the root-like organs of parasites, such as dodder and 

 mistletoe, which grow into the tissues of the host plant and connect the 

 tissues of the parasite with those of the host. Such roots are also called 

 haustoria. Through them pass not only water and inorganic salts but 

 also foods made by the host plant. 



When the seedling of the common dodder, which is a mere thread- 

 like stem two or three inches in length, comes in contact with a living 

 green plant, it coils about it and a row of haustoria develops wherever 

 the stem is in contact with the host. The haustoria penetrate between 

 the cells of the host plant to the water-conducting and food-conducting 

 tissues ( Fig. 120 ) . The dodder then grows rapidly, branches, and makes 

 new contacts; and its haustoria penetrate the tissues of other parts of 



