CHAPTER XII. 



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 development. The great 

 majority of plants have this ability. They build up their substance 

 by assimilation of simple inorganic materials derived from the environ- 

 ment. (See Chap. VIII., p. 147.) To such a type of nutrition, depen- 

 dent on inorganic raw materials, the term Autotrophic is applied. 



While the typical plant thus depends on an autotrophic nutrition, 

 a number of plants have not the ability to assimilate purely 

 inorganic materials : hence they must have at their disposal a supply of 

 organic substances before growth is possible. The nutrition of these 

 plants is said to be irregular or Heterotrophic. Some plants are wholly 

 dependent on irregular nutrition, others are only partially dependent 

 on it. Organic food can only be derived from some other organism, 

 living or dead. If this food is taken from a living organism, plant or 

 animal, this organism is called the Host, while the dependent organism 

 is called a Parasite upon it. 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. 

 Parasitic and saprophytic plants frequently show marked modifica- 

 tions of form, usually regarded as results of reduction. There is no 

 sharp line that can be drawn between these two conditions of para- 

 sitism and saprophytism, for sometimes the parasite causes death 

 but continues to feed upon the corpse, and so is first a parasite and 

 afterwards a saprophyte. A peculiar place is taken in this respect 

 by the Carnivorous plants which digest small animals. They capture 



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