OTHEK METHODS OF OBTAINING FOOD 211 



place on the ground, and the embryo grows to a length of 

 about an inch. Its apex attaches itself to the ground, and 

 the free portion moves round, describing a sort of spiral in 

 the air. If it comes in contact with a suitable host, ilr 

 twines round it after the fashion of a tendril, and numerous 

 suckers are developed in rows at the points of contact. 

 Haustoria spring from these suckers and penetrate the host, 

 extending inwards till they reach the wood (fig. 102). The 

 part below the attachment dies shortly after this relationship 

 has been established, and the parasite 

 is left attached to the host. In its 

 further growth it continues to twine 

 around the latter, putting out numer- 

 ous branches, which also form similar 

 coils, so that the host is completely 

 immeshed in the twining stems of the 

 parasite. -The latter bears no leaves 

 and possesses no chlorophyll in any 

 part, so that it derives all its food in 

 fully elaborated form from the tissues 

 of the host. Cuscuta produces num- 

 bers of flowers on its branches, and 

 from them are developed fruits and 

 seeds. The parasitism is complete, 

 and the relation frequently leads to the 

 death of the host which has' been 

 attacked. 



Parasitic plants are very frequently met with among the 

 fungi and the Bacteria. The former penetrate the living 

 cells 01 the plant they infest, or in a few cases ramify between 

 them, sending haustoria into the interior of the cells between 

 which the mycelium grows (fig. 103). They make use of the 

 contents of the cells, destroying and absorbing the living sub- 

 stance as well as any formed materials which may be present. 

 In many cases also they destroy the cell-walls, and utilise 

 the carbohydrate materials of which the latter consist. 

 Their ravages only cease with the death of the organism. 



U* 



FIG. 103. CELLS OF POTATO 

 PLANT INFESTED WITH 

 Phytophthora. 



b, hypha running between 

 the cells and sending 

 haustoria (a) into their 

 interior. 



