220 



VEGETABLE PHYSIOLOGY 



all its food in fully elaborated form from the tissues of the 

 host. Cuscuta produces numbers of flowers on its branches, 

 and from them are developed fruits and seeds. The para- 

 sitism is complete, and the relationship 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 of 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. 107). They 

 make use of the contents of the cells, 

 destroying and absorbing the living 



FIG. 107. CELLS OF POTATO J 



PLANT INFESTED WITH substance as well as any formed 



Phytophthora. i i i i T 



, , materials which may be present. In 



ft, hypha running between J 



the ceils and sending many cases also they destroy the 



haustoria (a) into their ,, ,, _ . .,. , 



interior. cell-walls, and utilise the carbo- 



hydrate materials of which the latter 



consist. Their ravages only cease with the death of the 

 organism. 



The power of living plants to assimilate the food 

 manufactured by others is taken advantage of in the 

 processes of grafting and budding. In these operations a 

 slip of a particular plant is inserted into a wound made 

 in another nearly related one, and the two are closely 

 bound together. The graft or scion comes into such close 

 connection with the stock that the food which is contained 

 in the cells of the latter passes into the tissues of the graft, 

 which thus receive their nourishment. After a 'longer or 

 shorter time the two become so completely united that they 

 live subsequently as a single organism, and the processes 

 of carbohydrate and proteid construction proceed as in a 

 normal plant. 



