A MANUAL OF ]iOTANY 129 



cells are, in all probability, an alga yon have studied, and 

 the lichen is really a mutual partnership of a fungus and an 

 alga. What advantage does such a plant have over a fungus ? 

 The fungus iihiinents are attached to the algLc cells hy tiny 

 rootlike structures called the haustoria. Of what benefit 

 would the ])artn('rship be to the alga ? This mutual relation- 

 ship is called sj/mbiosis, and often exists anujng animals. The 

 bacteria have a similar relationship with clovers and related 

 plants. 



Reproduction. Observe on some specimens, elongated 

 clubs, cups, or urnlike structures. These are the fruiting 

 bodies or apotheda. Study a section of an apothecium (Jip), 

 and observe the filaments ending in spore cases (asci). How 

 many s[)ores in each case ? What are the s])ores for ? 



Drawings. Draw details of lichen structure and a sectional 

 diagram of an apothecium. 



Value of lichens. From any source find out any value to 

 man directly or indirectly which this group of fungi has. 

 Look u}), in particular, reindeer moss, Iceland moss, rock 

 tripe, and litmus. What relation have lichens to soil forma- 

 tion ? 



A Field Study of Algce and Fungi 



Take a limited area, if possible, containing as great diver- 

 sity of surface features (meadow, wood, pond, creek, sand, 

 gravel banks, bluffs, etc.) as your neighborhood will afford. 

 Make a careful nmp, drawn to a large scale, of the 

 district, denoting by various tints the various features of 

 topography. 



Explore very carefully for any alga^, fungi, or lichens, and 

 designate the location of the same by letter or figure on your 

 map. 



Having found as many forms as })ossible, summarize the 

 whole by a table having the following headlines : — 



