TRANSACTIONS OF SECTION E. 735 



and prostrate trunks of trees, showing that the country was forested. To this 

 succeeds wet spongy peat as before, to be again covered with dry peaty soil and 

 tree trunks, &c., and so on. From an examination of the plant-remains in these 

 formations, Prof. Blytt draws the following conclusions: — 



The Norwegian flora began with an immigration of Arctic plants during a dry 

 period, evidence of which he finds in the presence of the remains of these beneath 

 the lowest layer of peat. As the climate became warmer and the land rose, a 

 rainy period set in, accompanied by an immigration of sub-arctic plants (juniper, 

 mountain ash, aconites, Sec), which to a great extent replaced the Arctic 

 flora, which is impatient of great wet. This was the period of the flrst peat-bog 

 formation. It was followed by a dry period, during which the bogs gradually dried 

 up ; while, with the increasing warmth, deciduous trees and their accompanying 

 herbaceous vegetation were introduced. The succeeding rainy season produced 

 a second peat-formation, killing and burning the deciduous trees, the increasing 

 warmth at the same time bringing in the Atlantic flora, characterised by the holly, 

 foxglove, and other plants ilow confined in Norway to the rainy Atlantic coast. 

 To this succeeded a third period of drought, when the bogs dried up and pine 

 forests with their accompanying plants immigrated into Norway, to be in like 

 manner destroyed and buried by bog earth during the next following rainy period ; 

 and it was during these last alternations that the subboreal plants now affecting 

 the lowest south-eastern districts of Norway were introduced ; and the sub-atlantic 

 plants, the most southern of all the types, which are confined to the extreme south 

 of the country. 



It would be premature to regard all Prof. Blytt's recurrent periods as irrefrag- 

 ably established, or his correlations of these with the several floras as fully proved ; 

 but there is no doubt, I think, that he has brought forward a vera cmma to account 

 for the alternation of dry country with wet country plants in Norway, and one that 

 must have both actively promoted the first introduction of these into that country 

 and also influenced their subsequent localisation. It would strengthen Prof. Blytt's- 

 conclusions very much, if his alternating periods of rain and drought should be found 

 to harmonise with Mr. CroU's recurrent astronomical periods, and with Mr. Geikie's 

 fluctuations of temperature during the decline of the glacial epoch : so would also 

 the finding in the bogs of Scotland a repetition of the conditions which obtain in 

 those of Norway ; and there are so very many points of resemblance in the physical 

 geography and vegetation of these two countries, that I do not doubt a comparison 

 of their peat-formations would yield most instructive results. 



Thus far all the knowledge we have obtained of the agents controlling geo- 

 graphical distribution have been derived from observations and researches on 

 northern animals and plants, recent and tertiary. Turning now to the southern 

 hemisphere, the phenomena of distribution are much more difficult of explanation. 

 Geographically speaking there is no Antarctic flora except a few lichens and sea- 

 weeds. The plants called Antarctic,' from their analogy with the Arctic, are very 

 few in number.and nowhere cross 62° of south latitude. They are, in so far a"s 

 they are endemic, confined to the southern islands of the great southern ocean, and 

 the mountains of South Chili, Australia, Tasmania, and New Zealand ; whilst the 

 few non-endemic are species of the nearest continents, or are identical with tempe- 

 rate northern or with sub-arctic or even Arctic species. Like the Arctic flora, the 

 Antarctic is a very uniform one round the globe, the same species, in many cases, 

 especially the non-endemic, occurring on every island, though there are sometimes 

 thousands of miles of ocean between the nearest of these. And, as many of tlie 

 island plants reappear on the mountains above mentioned, far to the north'of their 

 island homes, it is inferred on these grounds, as well as on astronomical and geo- 

 logical, that there was a glacial period in the southern temperate zone as we'll as 

 in the northern. 



The south temperate flora is a fourfold one. South America, South Africa, 



' For accounts of the Antarctic fiora see the Botany of the Antarctic Expedition 

 of Sir James Ross, where the relations of the floras of the southern hemisphere with 

 tlie Antarctic are discussed in introductorj- cliapters. 



