chap. iv Taxonomy, 1860-1900 113 



Baranetzky's results were confirmed and extended by 

 Treub in 1873 and by A. Moller in 1887. Reess, in 1871, 

 found it possible to start the formation of a Collema 

 thallus by germinating some spores of the lichen among 

 cells of Nostoc lichenoides, and Bornet afforded further 

 proof in 1873 by obtaining a lichen in consequence of 

 sowing spores of Parmelia among cells of Protococcus. 

 Bonnier in 1889 extended these results by many careful 

 synthetic cultures. The fact that fungi of quite different 

 families may be concerned in the formation of a lichen was 

 proved in 1881 by Mattirolo, who showed that the fungus 

 of Cora is one of the Basidiomycetes, while all previously 

 noticed belong undoubtedly to the Ascomycetes. The fructi- 

 fication till then associated with the Lichen as an organism 

 was exactly similar to those of the latter group. 



The nature of the relationship was at first, and naturally, 

 held to be one of parasitism, in consequence of the known 

 incapacity of fungi to lead an independent life. Later investi- 

 gations, however, revealed its true nature to be symbiotic. 



Stahl made a very complete investigation into the 

 structures concerned in the reproduction of lichens in 1877. 



In his classification of the Vascular Cryptogams Sachs 

 laid stress on heterospory as a diagnostic feature of what 

 he held to be natural groups. He distinguished three 

 wholly isosporous divisions, Filices, Equisetaceae, and 

 Ophioglossaceae ; while he recognized two groups which are 

 partly heterosporous, Rhizocarpeae and Lycopodiaceae. 

 He was inclined to class the Marattiaceae with the Ophio- 

 glossaceae, on account of the resemblances between the 

 sporangia of both. In further subdivision of the Filices 

 he followed in the main the classification of Mettenius 

 in 1856, recognizing as subdivisions : Hymenophyllaceae, 

 Gleicheniaceae, Schizaeaceae, Osmundaceae, Cyatheaceae, 

 and Polypodiaceae, but relegating as we have seen the 

 Marattiaceae to another division. 



GREEN H 



