SUMMARY OF THE SAC FUNGI 



257 



along storm-swept seacoasts. Some forms actually cover large 

 areas, as the reindeer moss (Cladonia rangiferina, Fig. 227, A), 

 which in extreme northern countries furnishes an important 

 source of food for herbivorous animals, as the reindeer. Since 

 the lichens are the first plants to grow on exposed rocks, they 

 form there the first soil, mingled with decayed vegetable matter 

 (humus), which may furnish a foothold for higher plants, such as 

 the mosses and grasses, 

 that are constantly try- 

 ing to establish them- 

 selves in the territory of 

 the lichens. 



Some uses of lichens. 

 Some lichens (Roccella) 

 yield beautiful purple, 

 blue, and crimson dyes 

 called orchil and cud- 

 bear, much used in 

 former centuries in 

 Italy, and later in other 

 parts of Europe. Orchil 

 when prepared with 

 soda or potash yields 

 the dye litmus, em- 



-i i ,1 P A, the reindeer moss (Cladonia rangiferina) ; 



ployed in the manufac- B> Cladoniacornucopioides- C, Usneabarbata; 



ture of litmus paper, s, sac fruits 



Other lichens, as Iceland moss (Cetraria), are ground up and 



mixed with wheat and made into cakes. 



272. Summary of the sac fungi. The most remarkable fea- 

 ture of the life history of the Ascomycetes is the position of the 

 ascocarp as a sporophytic phase following the sexual process 

 and alternating with sexual plants, or gametophytes. The asco- 

 carp holds a place in the life history similar to that of the 

 cystocarp in the red algse (Sec. 246). There are numerous types 

 of asexual spores (such as conidia) in the Ascomycetes, which 



FIG. 227. Some branching, or fruticose, 

 lichens 



