446 



opment of lichens. It is practically impossible to determine what 

 free fungi are identical with the fungi of lichens. All investigators 

 in this line have met with very unsatisfactory results, a thing natur- 

 ally to be expected. According to Tavel* the fungi of the Colle- 

 maceae, Arthoniae and Lecideaceae are more or less closely re- 

 lated to the Patellariaceae. The relationship of the fungi of the 

 Pertusariae, Lecanareae, Pannarieae, Umbilicarieae, Peltidiaceae^ 

 Parmeliaceae, Usneaceae, Cladoniaceae, Sphaerophoreae, Ephebeae 

 and Lichineae is practically unknown. The Verrucarieae, De- 

 campieae and Endocarpieae are related to the Amphisphaeriae, 

 Sphaerelloideae. Such uncertainty is certainly very unsatisfactory 



Although there may be algae, such as Cystococcus Jminicolay 

 Pleurococciis vulgaris, Nosioc lichenoides, etc., which only await the 

 opportunity to unite with some fungus to form a lichen, yet it is 

 evident that no true Ascomycete has the power to enter into such 

 a union. There is great uncertainty as to the exact method by 

 which the first lichen or lichens were formed. The author makes 

 the following hypothetical assumption : " In the beginning several 

 lichens were formed by the union of true fungi with algae. Ac- 

 cording to Mollert such a process is now going on in the case of 

 Cora pavonia and the related forms of Dictyoncma and Laiidatea 

 The gelatinous lichens are very likely the oldest forms of the 

 Ascolichenes. Such a gelatinous lichen took its origin as the re- 

 sult of the parasitic union of a fungus and a spherical colony of 

 No stoc lichenoides.' The question of the origin of the fungus coin- 

 cides with the question of the phylogenetic origin of parasitic 

 fungi in general and need not be further discussed. The fungus 

 which at first behaved like a true parasite (antagonistic symbiosis) 

 took its entire food-supply from the nostoc. The condition of 

 mutualism (consartism) was a phylogenetic product ; perhaps due 

 to natural selection or other formative causes resulting from 

 the union of alga and fungus. From this ^ro\.o-Collenia other 

 gelatinous lichens were evolved ; finally also such with hetero- 

 merous thallus. It is probable that in the course of phylogenetic 



*Tavel, F. Vergleichende Morphologic der Pilze, pp. 94 and 108. Jena^ 

 1892. 



f Moller, A. Ueber die eine Thelephoree, welche die Hymenolichenen : Cora 

 Diciyonema wad. Latfdatea bildet. Flora 77 : 254-278. 1893. 



