27 



Chens is very doubtful. The Collemaceae include the Lichenes Ho- 

 moeomerici or Gelatinosi of previous authors, and the Lichenacese all 

 the rest. The first tribe is divided into two series, the Lichinei 

 (fruticulose) and the Collemei (subcrustaceous, scaly and frondose) ; 

 the third into six serieSv Epieoniodei (Caliciei), Cladoniei, Eama- 

 lodei, Phyllodei, Placodiei and Pyrenodiei, and these into nineteen 

 tribes. Minor importance is attached to spore characters in estab- 

 lishing Genera, so far as color and the internal divisions are con- 

 cerned. Thus Lecanora and Rinodina constitute but one genus, 

 and Verrucaria includes Pyrenula and many other genera of various 

 authors. So great has been the accumulation of material and the 

 advance of knowledge since that time, that perhaps this classifica- 

 tion does not represent his present views. His knowledge of the 

 world lichens exceeds that of any other person. Next to him in 

 this respect stands Dr. J. Mviller of Geneva. But their views are 

 very confiicting. Both seem disposed to multiply species to excess, 

 Nylander relying largely on chemical reactions and Mriller on spore 

 diflferenees. Each has contributed largely to the knowledge of ex- 

 otic Lichens. The Lichens of Aeharius and the other earlier Li- 

 chenists have been studied in the light of modern science, and a 

 knowledge of the results thus obtained is necessary in regard to 

 their work, especially with the lower Lichens, in which so much de- 

 pends on the characters of the spores and the gonidia. 



In this very brief sketch we have necessarily omitted many dis- 

 tinguished names and works. "We have already referred to the ear- 

 lier labors of Tuckerman. Becoming a zealous student of the mi- 

 croscopical characters of Lichens, he afterwards followed Nylander 

 in his descriptions of Cuban and North American Lichens in the 

 Proceedings of the American Academy of Sciences, but gradually 

 came to systematic conclusions of his own, which were first hinted 

 at in his Lichens of California, (1866,) and were fully developed in 

 his Genera Lichenum, (1872,) and applied in the first part of his 

 Synopsis, (1882,') in the introduction to which last he indicated that 

 he had at least partly accepted the views of Dr. Minks. The com- 

 pletion of his Synopsis was prevented by his death is 1866, and 

 there is no one left to take his place. He had not paid much at- 

 tention to the physiology of Lichens, his rank being that of a philo- 

 sophical Systematist, and his leading aim being to give expression 

 to a larger and better conception of species than prevailed with the 



