PERIOD VI. 1846-1867 17 



the question, and regarded as personal enemies those who dared to differ 

 from him. The last years of his life were passed in complete solitude. He 

 died in March 1899. 



Owing to the Very inadequate powers of magnification at the service of 

 scientific workers, the study of lichens as of other plants was for long restricted 

 to the collecting, examining and classifying of specimens according to their 

 macroscopic characters ; the microscopic details observed were isolated and 

 unreliable except to some extent for spore characters. Special interest is 

 therefore attached to the various schemes of classification, as each new one 

 proposed reflects to a large extent the condition of scientific knowledge of 

 the time, and generally marks an advance. It was the improvement of the 

 microscope from a scientific toy to an instrument of research that opened 

 up nev/ fields of observation and gave a new impetus to the study of a group 

 of plants that had proved a puzzle from the earliest times. 



Tulasne was one of the pioneers in microscopic botany. He made 

 a Methodical study of a large series of lichens^ and traced their develop- 

 ment, so far as he was able, from the spore onwards. He gave special attention 

 to the form and function of spermogonia and spermatia, and his work is 

 enriched by beautiful figures of microscopic detail. Lauder Lindsay^ also 

 published an elaborate treatise on spermogonia, on their occurrence in the 

 lichen kingdom and on their form and structure. The paper embodies the 

 results of wide microscopic research and is a mine of information regarding 

 these bodies. 



Much interesting work was contributed at this time by Itzigsohn^ 

 Speerschneider'*,Sachs^,Thwaites'', and others. They devoted their researches 

 to some particular aspect of lichen development and their several contribu- 

 tions are discussed elsewhere in this work. 



Schwendener' followed with a systematic study of the minute anatomy 

 of many of the larger lichen genera. His work is extremely important in 

 itself and still more so as it gradually revealed to him the composite 

 character of the thallus. 



Several important monographs date from this period : Leighton* reviewed 

 all the British " Angiocarpous " lichens with special reference to their 

 " sporidia " though without treating these as of generic value. He followed 

 up this monograph by two others, on the Graphideae^ and the Umbili- 

 carieae^", and Mudd" published a careful study of the British Cladoniae. 

 On the Continent Th. Fries'^ issued a revision of Stereocdulon and Pilo- 

 phoron and other writers contributed work on smaller groups. 



' Tulasne 1853. ^ Lauder Lindsay 1859. ^ Itzigsohn 1854-1855. ■* Speerschneider 1853. 



' Sachs 1855. * Thwaites 1849. '' Schwendener 1863-1868. * Leighton 1851. 



" Leighton 1854. " Leighton 1856. " Mudd 1865. '^ Th. Fries 1858. 



S. L. 



