DERIVATION OF THE FLORA AND FAUNA 263 



The systematical position of Callitriche has been discussed many times, but 

 we know nothing of its history or where it started. The genus is world-wide, but 

 many species are not wide-spread and some are quite local, among them C. Lech- 

 leri, which may have been carried to Juan Fernandez from the mainland by 

 accident. 



The tribe Colletieae of the otherwise wide-ranging Rhamnaceae is called 

 austral-antarctic by Sussengut (Xaturl. Pflanzenfam. 2nd ed.); except Adolphia 

 (Mexico-U.S.A.) the genera are distributed over Andean and extratropical S. Amer- 

 ica, centering in Chile, and Colletia spartioides finds its place with the Andean 

 element. It should be mentioned that Discaria (ii) extends south to Fuegia and 

 reappears in Australia (i) and New Zealand (i), suggesting transantarctic migra- 

 tion from America. 



The family Flacourtiaceae is tropical; Azara is neotropical with about 19 

 species in Chile, i in Brazil and i in Argentina. The tribe to which it belongs 

 is well developed in the south hemisphere: tropical America and Africa, Mada- 

 gascar and neighbouring islands, Asia, New Guinea and [Xylosma] Oceania to 

 Hawaii, but Antarctica may not at all be involved in its history. 



Myrtaceae. A very large world-wide and tropical-subtropical family. Of the 

 subfamily Myrtoideae, some 2400 species, 75 % are American, the remainder scat- 

 tered over Asia, Africa, Australia and Oceania. The Leptospermoideae, some 850, 

 are restricted to Australasia with the single exception of Tepualia, monotypical 

 and endemic in the Chilean rain forests, south to West Patagonia, a most inter- 

 esting case of disjunction. Berry [26] regards the family to be of American ori- 

 gin and to have attained its present distribution before the close of the Creta- 

 ceous. Basing his conclusions on fossil evidence he thinks that during the cooling 

 down of the climate during late Tertiary, the ancestral stock of Myrtoideae with- 

 drew from North America to the neotropical zone; the Australian Leptospermo- 

 ideae represent the remnants of the Cretaceous radiation during which numerous 

 new types became evolved. Some of these eventually invaded Antarctica and 

 Tepualia survives on Chilean soil. 



The Juan Fernandez Myrtoideae are closely linked to Andean types. For Ugni 

 Selkirkii ^v\d Myrteola Tiuniinularja see p. 206. NotJiomyrcia, now restricted toMasa- 

 tierra, may or may not have inhabited a larger area. Myrceugenia has about 20 

 species in Chile. 



Gunneraceae (often placed as a subfamily under Halorrhagidaceae) is a classi- 

 cal example of a tricentric Antarcto-tertiary type. Its long and complicated history 

 is reflected in its taxonomic differentiation; 6'/<';/;7^r<^ is composed of 6 subgenera. 

 Pangue is the largest with 10 species ranging from Costa Rica to S. Chile, i in 

 Brazil, 3 in Juan Fernandez and 2 in Hawaii. Perperisuvi is monotypical with 

 separate varieties in S. Africa, British E. Africa and Madagascar, Ostenia an aber- 

 rant monotype endemic in Uruguay. Misandra includes 3 species, one extending 

 from Colombia to Fuegia and Falkland, one restricted to the S. Chilean Andes 

 and one to subantarctic America; Milligajiia has 8 species in New Zealand and 

 I in Tasmania. The monotypical Pseudogmmera inhabits New Guinea, Java, Su- 

 matra and the Philippines. No subgenus is found in more than one sector. It is 



