DECEMBER. 29 



the other hand, were I to lay out on a table a series of 

 specimens collected at various localities and elevations, 

 from the shores of Otago Harbour to an elevation of 

 ($000 feet 01- 7000 feet on one of the western mountains, 

 it would puzzle a systematist to say to what species some 

 of the intermediate forms belonged. What is perhaps of 

 more interest is this, that Coriaria ruscifolia is as common 

 in Chili as in New Zealand, while C. thymifolia ranges 

 from Peru to Mexico along the main chain of the Andes at 

 elevations of from 4000 feet to 12,000 feet. This recalls to 

 some extent the distribution of the Fuchsias, except that 

 the New Zealand species of the latter are quite different 

 from the South American. Both of our species of tutu 

 occur in the Kermadec Islands, which lie pretty far to the 

 north of the New Zealand group of islands. These facts 

 point to the antiqiiity of the species, while the distribution 

 of the genus bears out the same idea still more. Species of 

 Coriaria occur in Southern Europe, Japan, China, and the 

 Himalayas ; indeed Linnaeus gave the generic name to 

 the plant, because the roots of the European species 

 (C. myrtifolia) have long been used in Southern Russia 

 and elsewhere for tanning leather.* Now if one might 

 hazard an interesting speculation, I would suggest that 

 in a former geological age Coriaria was spread over the 

 extreme north of the northern hemisphere at a time when 

 the climate of Spitzbergen was that of a temperate region. 

 When the great ice-caps of the last or some preceding 

 glacial epoch began to settle on the North Pole, driving 

 the vegetation southwards, Coriaria had to retreat along 

 with other plants. It appears to have followed two lines 

 of retreat, one down to Southern Europe, and another 

 through the Alaskan or Behring Sea region, this latter 

 probably dividing into two branches, a western line passing 

 down by Japan and China to the Himalayas, and an eastern 

 down the mountain chains of America, from whence it 

 spread across the Pacific to New Zealand by a now sub- 

 merged chain of communications. Such speculations are 



* Latin, Corinin, leather. 



