ROOTS AND THEIR USES l8i 



new suckers are formed from time to time, which, Hke the 

 sucker formed in the first season, grow inward through the 

 tissues of the host until they reach the wood. Thus, while 

 the suckers of the dodder take materials both from the bast 

 and from the wood, the suckers of the mistletoe make con- 

 nection only with the wood of the host, whence they absorb 

 water and simple salts. Having green leaves, the mistletoe 

 takes carbon dioxid from the air and manufactures for itself 

 the more complex foods which the dodder takes from the 

 host plant. The American mistletoes are similar to the 

 European form in their manner 

 of growth and of obtaining food, 

 but are smaller plants. One of 

 them is also used, though less ex- 

 tensively, for Christmas decora- 

 tions. 



Among the most remarkable 

 parasitic plants are the Rafflesias 

 and their relatives (Fig. 113). 

 Their vegetative body consists Fig- 113- — One of the Raf- 



only of a network of thread-like ^^^'\ ^^'"''^ {Brusmansia), 



growing as a parasite on the 

 rows of cells, very much like the roots of Cissus. After Kemer. 



body of a fungus ; this network 



lives and grows between the bark and the wood of prostrate 



stems and roots. The only part of the parasite that appears 



outside the tissues of the host is the large flower. That of 



one species of Rafflesia, found in Stimatra, is said to be the 



largest flower borne by any plant. When fully open, it has 



a diameter of three feet. 



202. Mycorhizas. — A curious relation exists between 



many forest trees, including oaks, maples, poplars, and most 



of the conifers, and certain fungi whose branching threads 



are found living upon small branch roots of the trees. The 



fungous threads form a thick felt over the surface of a root ; 



separate threads grow in between the cells of the cortex, and 



