272 



GENERAL MORPHOLOGY OF PLANTS 



or less loosely attached. A common one on board and rail fences 

 as well as on other woody structures is the star-shaped Physcia 

 (Physcia stellaris). The plant is circular, rather closely appressed 

 to the wood, and the margin is radiately divided into narrow 

 irregular lobes, giving it a star-shaped form. It is dull gray in 

 color. Scattered over the central portion are a number of cup- 

 shaped or saucer-shaped bodies, the fruit bodies, or the apothecia, 

 as they are called in the lichens. This fruit body is like that of the 

 cup fungi. The sacs or asci are mingled with numerous sterile 

 hyphae (paraphyses) which overtop the asci and broaden out, thus 

 forming a covering (epithecium) over the ends of the asci.* Par- 

 melia is another very common foliaceous lichen growing on rocks, 

 sometimes very common on small stones in the field. Peltigera 

 is a common one growing on leaf mold in the forest. 



434. The fruticose lichens. These are more or less erect 

 forms and often very much branched. Some species of Cladonia 



grow on rotting wood, and 

 one species with bright red 

 rounded tops is very com- 

 mon on rotten stumps and 

 logs. The bright red bodies 

 are the fruit bodies (apo- 

 thecia), which here are 

 arched instead of cup- 

 shaped. Another species 

 of Cladonia (C. rangiferina) 

 is the reindeer moss. It 

 profusely branched 



Fig. 236. 



Fruticose lichen (Cladonia cristatella), thallus 

 grayish green, the tips bright red. Grows on 

 rotten logs, etc. Natural size. 



IS 



into slender grayish green 

 branches. It is very com- 

 mon on the ground of the arctic tundra, sometimes covering 

 extensive areas. It is eaten by the reindeers. Another common 



* The fruit body of the lichen is the ascoma. The sterile wall outside of the 

 group of asci is the excipulum; the broadened ends of paraphy ses united above 

 the asci form the epithecium; the tissue beneath the asci is the hypothecium. 



