124 



GEOLOGY OF LA SALLE COUNTY. 



THE THALLUS AND APOTHECIUM. 



These were the only parts studied in the infancy 

 of the science. They contain many organs — such as 

 reg-ards the former a cortical layer of cellules; a g-oni- 

 dial layer of g-reen cells, and below filaments (hyphae), 

 then the hypothallus or fibrils. But as in Collema, 

 the thallus may be wanting-, or partly absent or scanty. 

 The apothecium on examination will be found to con- 

 tain g-onidia and the hymenicum which bears the thekes, 

 within which are the spores. There are also other 

 org*ans of various names and relations. The different 

 uses of these in the economy of the plant have beeu 

 the cause of speculations without number. The 

 microscope has pla3^ed an important part in their 

 study, and on the discoveries thus made have been 

 built up the systems of authors, beginning with Tow- 

 enfort about 1600, who first separated them from the 

 true mosses. Prom time to time, real or fancied, 

 improvements have been made by a number of eminent 

 men. Among them should be mentioned for Europe 

 Acharius, Elias Fries. Nylander. The latter has the 

 larg'est knowledge of world lichens of any man now 

 living, and may be said to be the first of lichenologists 

 in eminence. As to classification it will be long before 

 any system will be promulgated meeting general favor 

 by all. 



THE ECONOMIC USES OP LICHENS. 



These are many, and first impress the practical 

 man who cares nothing- for their scientific value. The 

 Iceland and Reindeer moss are best known and largely 

 used by whole populations in Europe. The hardy 

 hard}^ Laplanders are dependent upon the latter, espec- 

 ially for food for their animals; also spirits are made 

 frcm this Cladonia. Sticta pulmonaria was a specific 



