250 THE VOYAGE OF H.M.S. CHALLENGER. 



same plants are found to range from sea-level up to oOOO feet, and there is no real limit of altitude ; 

 even at 7000 feet elevation a thick cushion of moss, several inches in length, was found by the 

 German North Polar Expedition covering the ground. This remarkable condition in the Arctic 

 regions is mainly accounted for by Dr Pansch from the fact that, with the sun always near the 

 horizon in hi<di latitudes, the hill-slopes receive its rays nearly vertically, and thus receive more 

 radiant heat even than the flat land below them. There is little cooling at night, the clouds and 

 mist preventing radiation. 



" In Kerguelen Island, of course, in its low latitude, the inclined surfaces do not profit so much 

 by their inclination. There, as in the high north, the mosses and lichens are the highest plants in 

 range. In the successive groups of islands, Marion, Kerguelen, and Heard, they come lower and lower 

 down the mountain slopes, and in Possession Island, south of the Antarctic Circle, the few flowering 

 plants remaining below them at Heard Island have disappeared, and they are left growing alone. 



" In all the southern islands the density of the phanerogamic vegetation, the extent of develop- 

 ment of the individual plants, and the number of species present, decrease directly with the height. 

 The facts show how much more the constant absence of warmth, and a continuous moderately low 

 temperature, is inimical to plant development, than is periodical cold of the severest kind. In East 

 Greenland the condition of the vegetation in various localities depends more on the distance of these 

 from the ice barrier than on their position more or less north or south. The vegetation becomes 

 more abundant as progress is made inland, away from the ice-bound coast. Exactly the opposite 

 seems to hold in Kerguelen Island, where the chief source of warmth, though at the same time the 

 constant cause of the equalisation of temperature, is the sea, and where the accumulated snow inland, 

 and its attendant mists, render the soil there barren. In East Greenland, phanerogamic water-plants 

 are absent, because of the long freezing of the water in winter. In the southern island there is a 

 Limosella, and a lai'ge number of the other phanerogams seem to take on a special aquatic habit. 



" To return to Heard Island. At Corinthian Bay, large masses of sea-weeds were banked up on 

 the sandy shore, where I collected eight species, which have been described by Professor Dickie. 1 

 Amongst them were two new species — two which occur at Kerguelen Island, whilst the remainder 

 occur in Fuegia. The main mass appeared considerably different from the masses of algas found on 

 the Kerguelen shore. Durvillca utilis grew attached to the rocks under the cliffs, but the kelp 

 {Macroajstis pyriferci) does not grow at all about this group of islands, according to the sealers, which 

 is a remarkable fact, considering its great abundance at Kerguelen Island. 



" The sealers said that the climate of Heard Island was far more rigorous than that of Kerguelen 

 Island. In wiuter the whole of the ground is frozen, and the streams are stopped, so that snow has 

 to be melted in order to obtain water ; but in December, at Midsummer, there is plenty of sunshiny 

 weather, and Big Ben is often to be seen. It is possible to land in whale-boats on the average of 

 the whole year only once in three days, so surf-beaten is the shore, so stormy the weather." 



1 Juvrn. Linn. Sue. Lund., vol. xv. p. 47. 



