22 



lichens, doubtless the most comprehensive study of the subject ever 

 undertaken up to this time. Especially valuable are his observa- 

 tions in regard to the growth of lichens. His careful study of the 

 anatomy of these plants contributed very valuable aid to the future 

 classification of lichens. It is, however, especially interesting to 

 note that at this time (1858-1863) he was convinced that the gonidia 

 developed from the hyphae, as branches develop from the side of a 

 stem. In this he agreed with Bayrhoffer (5, 5a) and Speerschneider 

 (84). In the next period we shall find that he changed his opinions 

 as far as gonidia were concerned. Not much can be said in favor of 

 the illustrations accompanying Schwendeners communications. 



Another important work of the period was that of de Bary. 1 In 

 the work cited, this author gave a clear and concise description of the 

 minute structure of lichens. In many respects it resembled the work 

 of Schwendener ; in fact, a number of the illustrations were taken 

 from his work. De Bary gave a very comprehensive description 

 of the morphological and anatomical relations of the crustaceous 

 lichens. We cannot enter into a full discussion of de Bary's work ; 

 one opinion expressed by this author should, however, be referred 

 to in particular, since it has bearing upon the conclusions arrived at in 

 the next period. De Bary believed that some of the gelatinous 

 lichens (JSphebc, etc.) were either perfect or mature states of plants 

 whose immature states are recognized as forms of Nostoc, Chroococ- 

 cus, etc. ; or that these organisms are true algae, attacked by 

 certain ascomycetes, whose hyphae penetrate the algae and form 

 the lichen-thallus. From this we see that De Bary was the first author 

 to hint at the true nature of lichens. He also issued a very valu- 

 able communication in regard to the development of certain lichen- 

 spores (22). 



Considerable progress was also made in the chemical study of 

 lichens. Various substances peculiar to lichens were discovered, 

 such as cetrarin, variolin, orcin, erythrin, picroerythrin, evernin, 

 physodm, besides various acids, as cetraric acid, evernic acid, and 

 fatty acids. The alkaloids and acids discovered proved so 

 varied and variable that Schunk - came to the conclusion that one 



J De Barv, A. Morphologic und Physiologic der Pilze, Flechten und Myxomyceten. 

 Leipzig. 1866. 



2 Schunk, E. Einige Bermerkungen liber die von Stenhouse in der Rocella tinc- 

 toria and Evernia prunastri entdeckten Substanzen. Erdmann's Journal f ur practische 

 Chemie, 46 : 18-30. 1849. 



