NUTRITION OF PARASITES AND SAPROPHYTES 135 



210. Definition of a saprophyte. The fungi and bacteria 

 which are not parasites derive their carbohydrate food by grow- 

 ing on dead plants or animals or on their remains, that is, on 

 organic matter. Such plants are called saprophytes, plants 

 depending for their nutrition on dead or decaying organisms. 

 The largest number of species of both bacteria and fungi are 

 saprophytes, and many of them do very important work in the 

 household of nature, reducing the sub- 

 stance of dead plants to the condition of 



humus which improves the mechanical 

 condition of the soil, removes the bulky 

 parts of plants, and sets free many sub- 

 stances which can be used again for food 

 by the green plants. Examples of these 

 fungi are the mushrooms, toadstools, pun 7 

 balls, bracket fungi, molds, etc. 



NUTRITION OF PARASITES. 



Although the larger number of para- 

 sites are among the fungi and bacteria 

 there are many parasitic flowering 

 plants. A few of these are briefly de- 

 scribed here. 



211. Nutrition of the dodder. The 

 dodder, or "love vine" (Cuscuta), is a 

 slender twining plant which is parasitic 

 on clover, or some other cultivated plants 

 and on a great many weeds. There are 

 several species. The plant has very 

 inconspicuous flowers developed in 

 crowded clusters. The seeds are small. 



When the seeds germinate on the ground a root is formed which 

 attaches the plant to the soil. But when the slender vine twines 

 around the living stem of its host, at the places of contact it 

 develops wedge-shaped outgrowths which pierce the stem of the 

 host and penetrate the fibro-vascular bundles. These out- 



Fig. 9 8. 



Dodder, showing 

 twining around its he 

 patiens). 



stems 

 ; (Im- 



