12 GUIDE TO THE STUDY OF LICHENS. 



This in a nutshell is the great discovery of Schwen- 

 dener and which has revolutionized the study of 

 lichens. Reinke (1873) pointed out that the relation 

 of fungus and alga as it occurs in the lichen was not 

 ordinary parasitism ; that it indicated a relationship in 

 which both organisms were benefited. This relation- 

 ship he designated consortism. De Bary (1879) de- 

 scribed this phenomenon more fully and designated it 

 symbiosis, that is a "living together" for mutual 

 benefit. 



As a result of Schwendener's investigations lichens 

 were considered as fungi and were classified as such. 

 There was, however, great opposition to this method 

 of classification, especially on the part of the pure 

 systematists. In 1874 Stahl made a special study of 

 the spermagonia which led him to conclude that the 

 spermatia were the male fertilizing elements. Sturgis 

 (1890), an American scientist, seconded the conclu- 

 sions of Stahl. To Tuckerman we owe most of our 

 systematic knowledge of the American lichens. His 

 descriptions of species, carefully given, makes his 

 work the first that could be utilized by those of ordi- 

 nary capabilities. The style of Leighton's manual of 

 British lichens is peculiar ; the descriptions of species 

 are given in a peculiar mixture of English and Latin 

 which made it necessary for him to append an exten- 

 sive glossary of terms. Crombie (1895), also a Brit- 

 ish lichenologist, retains the same style. Hue (1892) 

 has published a list of lichens from which it may be 

 concluded that about four thousand species are known 

 at the present time. 



