262 C. SKOTTSBERG 



of the species inhabit extratropical S. America, but many of them are so closely 

 related that they are little more than microspecies and in not few cases based 

 on one or two specimens from a single locality, and the number of separable 

 taxa will perhaps be reduced when more material becomes available. Be this as 

 it may, 7 sections are represented in America, 5 in the Australian-N. Zealand 

 area, 3 are common to both, one of them ranging to the African sector, where 

 another section is endemic. As regards A. masafuera7ia see p. 206 above. I sup- 

 pose we can draw no other conclusion from this distribution than that Acaena is 

 an Antarcto-tertiary genus, 2 sections having developed numerous species in the 

 Andes and Patagonia. 



Margyricarpus, a small Andean genus, is so closely allied to Acaena that they 

 have produced a bigeneric hybrid in Juan Fernandez. Two more genera are found 

 in the Andes, Tetrag/ochiii and Polylepis. In S. Africa we have the large genus 

 Clijfortia. The remaining genera Sa^igiiisorba, Poteriuni and Benconiia (Macarone- 

 sia) belong to the N. hemisphere. 



Sophora sect. Tetrapterae is austral-circumpolar: New Zealand (3 species), 

 Chatham I. (1), Lord Howe I. (i). Austral Is. (i), Rapa (i), Marquesas (i), Hawaii 

 (i), Easter I. (i), Juan Fernandez (2), Chile (2; .S. macrocarpa, however, rather unlike 

 all the others), Diego Alvarez (i), and Reunion (i). With the exception oi niacrocarpa 

 and the Hawaiian cJirysopliylla the remaining species used to be united under 

 ictraptcra Ait., otherwise endemic in New Zealand. They are very closely related, 

 but distinct; it is of minor importance if we call them species or geographical 

 subspecies. Unless we believe that 5. telraptera was carried by water from island 

 to island and was transformed into a new species wherever it landed, we must 

 look upon Antarctica as a one-time centre of a polymorphous population, which 

 radiated in various directions; we shall not discuss here how this may have hap- 

 pened. We have not to do with litoral but with inland plants; the pods are 

 adapted to float, assisted by the four narrow wings, Jonow says, but some of the 

 forms have no wings at all, and even if they have, the pods open on the tree and 

 discharge their seeds. 



Fagara mayu and externa form their own section. When BCrger said [41. 19) 

 that Fagara had migrated to Juan Fernandez from the primeval forests of Peru 

 and Colombia he overlooked that the affinity is with palaeotropical rather than 

 with neotropical species; there are numerous species scattered from Australia and 

 New Caledonia to Polynesia and Hawaii, where many are endemic. Rutaceae were 

 perhaps represented in the Antarctic in Tertiary times, and we have too look for 

 a route across to the American sector. 



The family Euphorbiaceae is pantropical, let alone that Euphorbia has at- 

 tained a world-wide distribution and flourishes also in temperate climates. Dysopsis 

 is Andean, Seidelia (2) and Leidesia (i) South African, the fourth genus of the 

 Mercurialis group, Mercurialis (8), ranges from North P3urope to the Mediterranean 

 and is found in E. Asia. The southern genera seem to be more closely con- 

 nected mutually than with Mercurialis. The disjunctions are interesting and difficult 

 to explain, unless we can find good reason to look for a common source in the 

 Antarctic. 



