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C. SKOTTSBERG 



forcrotten that numerous green and bluegreen algae are cosmopolitan and that the 

 fungus spores as well as the thallogenous diaspore (in fact more important for 

 dispersal) of lichens are quite resistant and adapted to long-distance transporta- 

 tion, also that they have a greater facility to get established where they happen 

 to land than the spores of ferns and bryophytes. 



During early Tertiary times — and certainly much earlier — South America had 

 a rich and varied lichen flora of tropical and subtropical character. With the grad- 

 ual climatic differentiation and the evolution of cold-resistant forms the rising 

 Andes provided stations for both northern and southern lichens; migrations in 

 both directions helped to equalize the Boreal-arctic and Austral-antarctic floras and 

 furthered the origin of a bipolar element. 



With our present insufficient knowledge of the distribution of the lichens all 

 we can say with regard to a majority of species or genera is that they are tropi- 

 cal-subtropical or temperate and either northern or southern; it is rarely pos- 

 sible to decide in favour of the north or the south as a primary source of the 

 Andean temperate flora. The exceptions from this rule are few; for instance, gen- 

 era like Pachvphiale, Lcmmopsis and Massalongia may be classified as northern, 

 while Byssocauion, Psendocyphellaria, Xephroma and Stercocaukm are southern or, 

 if bipolar, have a southern centre making it permissible to conclude that the 

 Antarctic continent has played an important part in their history and that the 

 bicentric distribution of so many species, also in the larger genera, testifies to an 

 Antarctic origin or at least indicates that a transantarctic migration route once 

 existed. Thus I have ventured to distinguish an Antarcto-tertiary element also in 

 the Chilean-Juan Fernandez lichen flora. Here as in other groups the possibility 

 that a bicentric species may have reached its stations from the north must be 

 taken into account; that a circumglobal species has reached southern Chile and 

 New Zealand is no proof of a transantarctic connection. 



Below an attempt is made to distribute the Juan Fernandez lichens among 

 geographical-genetic groups. Only 164 species could be included. No place at all 

 could be assigned to many of the endemic species — see above p. 254 — and the fol- 

 lowing non-endemic ones with their disjunct areas were also excluded: Bacidia 

 delapsans, Usjiea dasypogoides diVidsiibton/losa, Caloplaca nib/ua, Bucllia haloplnloides 

 and fcrnaiidezimia. 



The arrangement proposed is far from satisfactory and will, I am sure, be 

 subjected to criticism. With our very imperfect knowledge of the real distribution 

 of lichens called "wide-spread" or even "cosmopolitan", mistakes in assigning a 

 species to a certain element are unavoidable. Thus, many were referred to group 

 I with great hesitation because it is impossible to decide if they have reached their 

 austral-bicentric stations (south Chile, New Zealand) independently from the north, 

 or if Antarctic routes are involved. The species lumped under IV surely represent 

 several different distribution patterns. 



