348 VEGETABLE PHYSIOLOGY 



the parasitic habit is associated with a degeneration of 

 structure, which especially affects the vegetative organs. 



The fungus which is parasitic in habit derives all its 

 nourishment from the plant or animal whose tissues it has 

 invaded. Other plants of the same group are not parasitic, 

 but live upon decomposing organic matter, being known 

 as saprophytes. Their mode of nutrition is, however, 

 essentially the same. They have all lost the chlorophyll 

 apparatus characteristic of the green plant, and cannot 



FIG. 146. Thesium alpinum, SHOWING THE SUCKERS ox THE ROOTS. 

 (After Kerner.) 



therefore work up the food materials that the latter absorbs 

 from the air. Instead, therefore, of absorbing carbon 

 dioxide, these plants take in their carbohydrate food ready 

 made in the form of an organic compound of some complexity, 

 which is usually some kind of sugar. Saprophytes can 

 absorb nitrogen in the same combinations as a green plant, 

 but they appear to utilise compounds of ammonia in pre- 

 ference to nitrates. No doubt their protoplasm is ultimately 

 fed with the same substances as is that of the higher plants, 



