300 



NATURE 



[JULY 30, 1 89 1 



debate ; yet we find that an active discussion is now 

 going on among Scandinavian botanists as to its eastern 

 or western affinities. Sir J. D. Hooker, in his " Outlines 

 of the Distribution of Arctic Plants," ^ made a careful 

 analysis of the species found in Greenland, and came to 

 the conclusion that the relationship was more European 

 than American, and this view seems to have been gener- 

 ally adopted by botanists. In a recent official report, 

 contained in the valuable series of memoirs published by 

 the Commission for the Exploration of Greenland,^ Prof. 

 E. Warming, however, has tried to show that the flora is 

 American ; and as this author has had access to fuller 

 materials than were formerly available, his opinion will 

 •carry considerable weight. Prof. A. G. Nathorst, a 

 botanist especially competent to speak on questions 

 relating to the botany of the Arctic regions and on the 

 relation of the recent Arctic flora to the Glacial epoch, 

 objects altogether to Prof. Warming's conclusions, and, 

 although deahng with the same materials, maintains 

 the accuracy of the generally accepted view as to the 

 European relationship of the vegetation.'* He also criti- 

 cally examines the flora in a way that has never been 

 done before, and points to its dependence on bygone 

 conditions. To certain of Prof. Nathorst's observations 

 and conclusions I should like to draw attention. 



The principal result arrived at by Prof. Warming was 

 that the boundary between the American and the 

 European provinces is formed by the Denmark Strait (the 

 strait between Greenland and America), and not by Davis 

 Strait as botanists have generally thought. This conclu- 

 sion Prof. Kathorst critically examines, and so many 

 curious and suggestive facts relating to geographical 

 distribution come out in this examination that 1 may be 

 excused for referring to certain of them somewhat in 

 detail. The flowering plants of Greenland include 386 

 species, none of which are confined to that country. 

 Leaving out of account circumpolar forms, Prof. Warming 

 finds in the list 36 characteristic western against 42 

 eastern species, but suggests that when the flora of Arctic 

 America is better known the balance will probably be in 

 favour of the western forms. Prof. Warming, however, 

 includes among the eastern plants only those now living 

 in Europe, the Asiatic-American species being classed as 

 western on the ground that they must have entered Green- 

 land from the west rather than from the east — a somewhat 

 unsafe line of reasoning when we take into account 

 former changes of climate and the local extinction of 

 many plants. 



Prof. Nathorst analyzes the list differently, and gives 

 most suggestive tables and a map of the local distribution 

 of the eastern and western plants in Greenland. From 

 these we find that the coast nearest to Iceland contains 

 European forms alone, the southern extremity contains 

 European forms in a majority, while the part of the west 

 coast nearest to America yields principally western 

 species ; but taking Greenland as a whole the flora is 

 more European than American. Another curious fact 

 noticed by Prof. Nathorst is that the American element 

 of the flora of Greenland is not entirely cut off by the 

 Denmark Strait, but extends eastward as far as Iceland. 



Prof. Warming considers that the nucleus of the present 

 flora of Greenland represents part of the original flora, 

 which was able to live through the Glacial epoch on the 

 non-glaciated areas ; but Prof. Nathorst points out that 

 the few non-glaciated mountain-tops must have been far 

 too high for any phanerogams to exist on them, and all 

 the lowlands were then covered with ice and snow. We 

 must therefore consider that both eastern and western 

 elements of the present flora of Greenland entered the 

 country in post-glacial times. The tables of distribution 



I 1 rans. Linn. Soc. vol. xxiii., pp. 251-348 (1861) ; partly reprinted (with 

 additirns) in the "Manual of the ISatural History ... of Greenland," 

 ■&C. (1875). 



'■" " Om Gr<^nlands Vegetation : Meddelelser om Gr(J)nland," Part 12 (1888). 

 3 Engler's botanischcn yahrbiich, 1891, p. 183. 



NO. I 135, VOL.44] 



show at what points a large number of the plants entered 

 — they came from the nearest land, whether European or 

 American. Whether in post-glacial times there was any 

 complete land-connection between Greenland and either 

 North America or Iceland is very doubtful, but the straits 

 may well have been narrower. The ice- foot, also, which 

 collects in winter beneath the sea-cliffs is placed in the 

 best possible position to receive any seeds or masses of 

 soil which may fall during the winter. This shore-ice is 

 drifted away in the spring, and may easily discharge its 

 burden on some far-distant shore uninjured, and the seeds 

 just ready to germinate. Winds, migrating birds, and 

 migrating mammals would all help to transport seeds 

 across the straits. 



Turning now to the British Isles, we know that a pro- 

 lific temperate flora inhabited this country in pre-glacial 

 times. We know also that this flora disappeared and was 

 replaced by a thoroughly Arctic one, at least as far south 

 as Norfolk, where its relics are found beneath the 

 moraines. Then came a period when Britain north of the 

 Thames was covered with ice and snow, and only an 

 occasional hill-top— or '' nuttatak" as it would be called 

 in Greenland — rose above. When the ice retreated, the 

 Arctic phanerogams again spread over the country, for we 

 find Salix Solaris, S. herbacea, S. reticulata, Betula nana, 

 and Loiseleuria procumbens in lacustrine deposits im- 

 mediately above the boulder clay near Edinburgh ; we 

 have also a similar flora, with Salix polaris, S. myrsinites, 

 and Betula ?tana, in Suffolk ; and even in Devonshire 

 the dwarf birch has been found. This stage, though its 

 flora is still imperfectly known, apparently corresponds 

 closely with the present condition of Greenland. 

 j In Britain, however, we have now reached a later stage 

 1 in the amelioration of the climate and re-seitlement of the 

 I country, for the Arctic plants have either disappeared 

 I entirely or have retreated to our mountain-tops, and in 

 I their place on the lowlands we find a temperate flora now 

 i living. The British flora, like that of Greenland, varies 

 according to the botanical character of the nearest land, 

 I though, as with Greenland, there is no reason, except the 

 I supposed impossibility of the migration of the animals 

 ! and plants without a bridge, to imagine that during post- 

 ! glacial times there has been any direct connection with 

 } the Continent, save perhaps at the Straits of Dover. The 

 ' distribution of plants in Britain is so peculiar that I may 

 be forgiven for pointing out to non-botanical readers that 

 we have a southern flora opposite France, a Germanic 

 flora on the east coast, a Lusitanian flora in the south-west, 

 and on the extreme west there are two American plants 

 unknown elsewhere in Europe. In the Britain of the 

 present day I believe that we may study the re-peopling 

 of a country over which everything has been exterminated ; 

 and until we have fuller direct evidence of the stages of 

 the process, we may safely accept Greenland and Britain 

 as illustrating the way in which Nature works to fill gaps 

 in the fauna and flora, whether these are caused by changes 

 of climate, by volcanic agency, or the submergence and 

 reappearance of islands. Clement Reid. 



THE SUN'S CORONA. 



SOME little time ago Dr. Schaeberle, of the Lick Obser- 

 vatory, was good enough to send me the following 

 letter :— 



Allow me to call your special attention to a note of miiie in 

 the forthcoming number of the A.S.P. Publicatioiis, entitled 

 *' Some Physical Phenomena involved in the Mechanical Theory 

 of the Corona." I wish to say that, as far as the connection of 

 this theory with the sun-spot peripd is concerned, there was not, 

 at any time, any effort on my part to make an agreement with 

 other theories, but the conclusions reached are the legitimate 

 and inevitable results of tracing certain observed phenomena to 

 unexpected explanations. As you will see, the logical outcome 



