i6 



Gyrophorae of Switzerland. The more important monographs, 

 however, were not issued until the following period. 



During this period little or no progress was made in the knowl- 

 edge of the anatomy and physiology of lichens. Although the com- 

 pound microscope had been introduced, little use was made of it. 

 This can readily be accounted for by the fact that the first compound 

 microscopes were very imperfect and also because, being an innova- 

 tion, they were regarded with distrust. Eminent opticians of the time 

 boldly declared that the compound microscope could never excel the 

 most perfect simple microscopes. 



Strange opinions were entertained in regard to the origin of 

 lichens. The belief in spontaneous generation and spontaneous 

 transformation was general. It will be instructive as well as amus- 

 ing to enter more carefully into some of the opinions entertained. 

 Hornschuch 1 occupied himself with the problems of " generation " 

 and " evolution." His opinions as far as they applied to lichens were 

 as follows : " Algae, lichens and mosses may develop without seed 

 from decomposing water. The decomposition of water induced by 

 warmth and sunlight gives rise to the common ancestral type of the 

 above vegetable forms. This ancestral type is a vegetable infusorium 

 known as Monas lens (green substance of Priestley) which, when 

 acted upon by light and air, undergoes an evolutionary transforma- 

 tion into alga, lichen and moss. Lichens are in reality mosses which 

 have been checked in their evolution and might well be designated 

 vegetable monstrosities. The apothecia (of lichens) are not the 

 fruit, but rather the beginnings of a corolla, analogous to the flower 

 of mosses (Moosroschen). The observations of Micheli in regard 

 to the development of lichens from soredia are to be discredited since 

 the discovery of the spontaneous generation of lichens." Sprengel 2 

 otherwise an accurate observer, believed that Lccidea immersa and 

 Monilia viridis were evolved from chaotic masses due to the action of 

 some force inherent in nature. The noted algologist Agardh 3 states 

 that he observed the transformation of Nostoc muscorum, var. lichen- 

 oides into Collema limosum. Nees von Esenbeck 4 was wont to lead 



1 Hornschuch, Dr. Einige Beobachtungen iiber das Entstehen der Algen, Flech- 

 ten und Laubmoose. Flora, 2 : 140-144. 1819. 



2 Sprengel, G. Ueber Bau und Natur der Gewachse. Halle. 1812. 



3 Agardh, C. A. Dissertatio de Metamorphosi Algarum. Lund. 1820. Flora,. 

 16: 17-41. (Beilage.) 1823. 



1 Esenbeck, Nees von. Handbuch der Botanik. 1820. 



