12 



about 1793, and his great work was issued about seventeen years later 

 (1810). This author divided lichens into three families according to the 

 structure of the thallus : I. Lichenes crustacei '; II. Lichenes foliacei; 

 III. Lichenes caulescentcs. Each of these families was again divided 

 into several tribes (twenty-eight in all) according to the structure and 

 position of the apothecia. He changed this system very materially 

 at a later period. 



It would be impossible to mention all lichenologists (including 

 collectors) of greater or less note. However we may state that they 

 made valuable collections at home and abroad and that their main 

 desire was to determine old or new species. Little or nothing was 

 done to ascertain the life-history of any of these interesting plants. 

 Lamarck 1 described one hundred and fifty-seven species besides a 

 number of doubtful forms. Jolyclerk mentioned and described three 

 hundred and sixty-five species, which was a fairly complete list of all 

 the lichens published at that time. It is, of course, impossible to know 

 whether this was the actual number of species discovered on account 

 of the numerous collections which were not published. 1 There is 

 also little doubt that many species published were duplicates. The 

 most active collectors were at work in Germany, France, Austria, 

 England and Switzerland. In 1802 it was admitted on good au- 

 thority that in all about five hundred species of lichens were known. 



In regard to the reproduction of lichens the controversy of the 

 previous period continued ; the question was still under discussion 

 as to what lichen structures should be considered as the male and 

 female organs. As in the previous period, these discussions and 

 conclusions were mainly based upon hypothetical assumptions. 



Hoffmann 2 agreed with Micheli that the soredia were the true 

 seeds of lichens, but further believed that it was not improbable that 

 the scutellae (apothecia) also contained seed ; lichens were thus sup- 

 posed to have a double means of reproduction. The true pollen 

 (fertilizing substance) was supposed to be hidden in the lichen, and 

 that fertilization took place internally during the early development 

 of the plant. 3 Gartner 4 perhaps came nearest the truth in regard 



1 Lamarck, M. de. Encyclopedic Methodique. Botanique, 3 : 470-50S. Paris. 1789. 



2 Hoffmann, G. F. Commentatio de Vario Lichenum usu. Erlangen. 1786. 



3 Hoffmann's general illustrated works on lichens are : 1. Enumeratio Lichenum. 

 Erlangen. 1784. 2. Descriptio et Adumbratio Plantarum. Classes Cryptogamica 

 Linnaei quae Lichenes dicuntur. Leipzig. 1790-1801. 



4 Gartner, J. De Fructibus et Seminibus Plantarum. 1788-1805. 



