CHAPTER XI 



IRREGULAR NUTRITION 



So far the Plant has been regarded as a self-supporting organism. 

 Starting from the seed with its small supply of food, it has been seen 

 to have the power of acquiring, from the soil and through Photo- 

 Synthesis, the material necessary for its own development. This is 

 the state of regular nutrition shown by most ordinary Plants. Such 

 Plants are called Autophytes, and their mode of life Autotrophic. Some 

 Families are composed entirely of these, for instance the Grasses and 

 Crucifers. • There is little doubt that complete self-nutrition was a 

 characteristic of the most primitive vegetation. 



But there are many plants which are Heterotrophic, that is, they 

 show some irregular or accessory method of nutrition. They are able 

 to derive organic nourishment from some source outside their own 

 body. Some such plants are only partially dependent upon irregular 

 nutrition, others are wholly dependent upon it ; while the method of 

 supply is also subject to considerable variety in different cases. For 

 instance, the food supply is sometimes taken from some other living 

 organism. This may be either a Plant or an Animal, and it is called 

 the Host, while the dependent organism is called a Parasite upon it. 

 But sometimes the dependent organism feeds not upon the living 

 host, but upon the dead body, or upon the products of its decay. 

 Such a dependent is called a Saprophyte. There is no sharp line that 

 1 can be drawn between these two conditions, for sometimes the parasite 

 I causes death, but continues to feed upon the corpse. Thus it would 

 jbe first a parasite, and afterwards a saprophyte. The converse may 

 also happen. A pecuhar place in this respect is taken by those 

 Carnivorous plants which digest small animals. They capture the 

 living animal, but feed upon its dead body. Other cases exist where 

 two organisms may live together with mutual tolerance, or advantage, 



187 



