308 



BOTANY. 



to completely evaporate before placing in the moist chamber. By tak- 

 ing precautions to keep out moulds, by suppl.yinj? the moist chamber with 

 air passed through one or two plujis of cotton-wool, he succeeded in 

 continuing the growth of the liyphae for three months, at the end of 

 which time the algae were surrounded by a good number of branches 



Pig. 818. 



Fig. 312. — Jlsneabarbata, nat. Bize. 

 to the bark of a tree.— After Sachs. 

 Pig. %IZ.—Slieta pulmonacea, nat. size. 



Fig. 213. 

 a, apothecia ; /, disk by which it is attached 

 a, apothecia.— After Sachs. 



of the hyphae, many of which had firmly attached themselves to the 

 cells of the algae. 



(c) The classification of lichens is by no means settled. 



The arrangement which is followed in this country is that of Profes- 

 sor Tuckerman.* He divides the order into five tribes, as follows: 



Tribe I. Pakmbliacbi. 



Apothecia rounded, open, scutelliform, contained in a thailine exciple. 



Family 1. TJsneei. Boccella, Bamalina, Daetylina, Oetraria, Ever- 

 nia, Usnea (Pig. 312), Alec oiia. Boecella linctoria and other species of 

 the genus furnish the dye known as orchil, and chemical test "litmus." 

 Ce'.raria islandica, the Iceland moss, is used both as a food and a medi- 



* Edw. Tuckerman : " Genera Lichenum ; An Arrangement of North 

 American Lichens," 1873, and " Synopsis of N. A. Lichens," 1883, 



