THE FUNGI. 



139 



References for Reading. Goebel's " Classification of Plants," pp. 

 100-114; Vines' "Text-Book of Botany," pp. 298-303; Bennett and 

 Murray's " Cryptogamic Botany," pp. 353-381; Bower's "Practical 

 Botany," pp. 470-472 ; Strasburger and Hillhouse's " Practical 

 Botany," pp. 269-271 ; Cooke's "Introduction to the Study of Fungi," 

 pp. 164-172 ; Bessey's " Essentials of Botany," pp. 155-165 ; Carpen- 

 ter's " The Microscope," pp. 571-574. 



The Lichens, often popularly mistaken for Mosses, 

 grow everywhere on stones, trees, fences, and the ground. 

 They are for the most part Sac Fungi ; a few belong with 

 the Toadstools. Until within recent years they were 

 thought to be independent plants, but they are now 

 known to be parasites of a very peculiar kind. The 

 plants upon which they grow belong to the lowest orders 

 of the green plants, such as Protococcus, Chroococcus, 

 Gloeocapsa, and Nostoc. The Fungi grow in such a way 

 that they entirely envelop the 

 host plant, which seems to gain 

 a decided advantage from the as- 

 sociation, so that it often grows 

 in places where it could not 

 possibly exist without the pro- 

 tection and moisture afforded 

 by the enveloping Fungus. Such 

 growth of plants in interde- 

 pendence upon one another is 

 known as symbiosis or commen- 

 salism. 



The thallus of the Lichen 

 sometimes clings closely to the 

 supporting surface. Such Li- 

 chens are called crustaceous. 

 (Fig. 78.) Sometimes the thal- 

 lus is flat, but has curled or crisped edges. Such Lichens 

 are called foliaceous. (Fig. 79, B.) Sometimes the Lichens 



FIG. 78. ^, Graphit 



crustaceous Lichen ; B, a 

 small portion of the same 

 more highly magnified; C, 

 Pertusaria Wulfeni, also a 

 crustaceous Lichen. (Goebel.) 



