PARASITES AND SAPROPHYTES 93 



between the food and the saprophyte. The roots of the 

 coral-root (Fig. 132) are covered with this fungus, and 

 the roots have practically lost the power of absorbing 

 nutrients direct. These fungus-covered roots are known as 

 mycorhizas (meaning "fungus root"). Mycorhizas are 

 © ^p^ not peculiar to saprophytes. They are found 

 *e& °©e>$i on many wholly independent plants as, for 

 c>^ e?%0 example, the heaths, oaks, apples and 

 *f» pines. It is probable that the fungus- 

 136. Bacteria, much threads perform some of the offices of rOOt- 

 magnified. hairg ^ the ^ Qn the other hand> the 



fungus obtains some nourishment from the host. The 

 association seems to be mutual. 



197. Some parasites are green-leaved. Such is the mistle- 

 toe. They anchor themselves on the host and absorb its 

 juices, but they also appropriate and use 

 the carbon dioxid of the air. In some 

 groups of bacteria the process of photo- 

 synthesis, or something equivalent to it, 

 takes place. 



198. Parasitism and saprophytism are 

 usually regarded as degeneration, that is, 

 as a loss of independence. The ancestors 

 of these plants might have been inde- 

 pendent. Thus, the whole class of fungi 

 is looked upon as a degenerate evolution. 

 The more a plant depends on other 

 plants, the more it tends still further to 



1 ., • j j 137. A parasitic fungus, 



lOSe ltS independence. magnified. The my- 



199. Epiphytes. — To be distinguished part!'"* sh<wraby the 

 from the dependent plants are those that ramiryingin the P ?e a! 

 grow on other plants without taking food haustoria projecting 

 from them. These are green-leaved plants shown. 06 The r Jong 

 whose roots burrow in the bark of the fungu°fhang f rom the 

 host plant and perhaps derive some food UJaf. 61 ? 



