2s6 



OUTLINES OF PLANT LIFE. 



the fungus is the master and the alga the slave. (See \ 48, 

 and figs. 215, 216.) The same fiingus may be found en- 

 slaving more than one species of algae even within the same 



mycelium. The proto- 

 nema of mosses (see ^ 

 59) or even the leaves of 

 some small plants may 

 be surrounded by a my- 

 celium. The enslaved 

 green plants are generally 

 unicellular or filamentous 

 algae. If the latter are 

 the species whose colonies 

 produce voluminous gela- 

 tin, the texture of the 

 lichen body is gelatinous ; 

 otherwise it is tough and 

 leathery. Some of the 

 fungi which ordinarily 

 associate themselves with 

 algae to form lichens may 

 exist free as saprophytes. 

 The alga itself influences 

 the form of the thallus more or less profoundly according 

 to its relative amount. The same fungus associated with 

 different algae produces lichens which are described as differ- 

 ent species, or even as different genera. 



368. 2. Animals and algse, — Helotism exists between 

 animals and algae. Various simple animals, such as radio- 

 laria, stentors, hydras, sponges, echinoderms, and worms, 

 enclose algae in their bodies and utilize the products of their 

 food manufacture. The algae thus enslaved are all minute 

 unicellular forms which multiply within the animal body by 

 fission (^ 260). 



Fig. 214, — ^A young clover plant, showing tuber- 

 cles, t, on the roots. Natural size. — After 

 Go£E. 



