CH. X] THE BASIDIA FUNGI 463 



masses of combined mycelium and Algse, scattered by the 

 wind. The ascospores are also carried by the wind, and 

 germinate on reaching suitable situations ; but the mycelium 

 is unable to continue its growth unless it comes into contact 

 with the suitable kinds of Algae. 



A very prominent Lichen is the so-called Reindeer Moss, 

 a fruticose form bearing its apothecia as brown spots at the 

 ends of the branches (Fig. 323). It abounds on northern 

 plains, where it constitutes the favorite food of Reindeer 

 and Caribou. The "Long Moss," which droops from the 

 dead branches of northern evergreen trees, is a fruticose 

 Lichen, though the superficially similar Long Moss, or Span- 

 ish Moss, of the southern trees is a flowering plant (page 535). 

 A foliose form, the Iceland Moss (Cetraria islandica) is some- 

 times used as food by natives of northern countries. Many 

 of the Lichens produce peculiar organic acids, which by 

 suitable treatment can be converted into bright pigments 

 useful in dyeing; and the litmus of laboratories is one of 

 these. 



Ecologically the Lichens are xerophytes, often living as 

 epiphytes. Since they lead all other plants in advance upon 

 barren places, their remains help to form a soil permitting 

 the advance of Mosses and other forms. Phylogenetically, 

 they are a composite group, brought into one for conven- 

 ience, as already noted (page 460). 



CLASS 10. BASIDIOMYCETES : THE BASIDIA FUNGI 



(Part of Eumycetes) 



These are the highest of the Fungi, and they include the 

 most destructive of crop parasites, the Smuts and Rusts, 

 together with the saprophytic Mushrooms, widely known 

 because edible. They differ from the Ascomycetes in a pre- 

 vailingly greater size and prominence of the spore-producing 

 bodies (as witness the Mushrooms and Puff balls), but chiefly 

 in the absence of any externally visible sexual processes. The 

 reproduction is effected mainly by the naked wind-carried 



