196 HEARD ISLAND. 



its rays nearly vertically on their surfaces, 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's Land, 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, Heard, they come lower and lower down 

 the mountain-slopes, and in Cockburn Island, south of the Ant- 

 arctic Circle, the few flowering plants remaining below them 

 at Heard Island have disappeared, and they are left growing 

 alone. At Cockburn Island the lichens range highest, and one 

 species reaches an altitude of 1,400 feet. 



In all the southern islands the density of the phanerogamic 

 vegetation, the extent of development 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. 



The condition of the vegetation in various localities in East 

 Greenland 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's Land, where the chief source of warmth, 

 though at the same time the constant cause of the equalization 

 of temperature, is the sea : and where the accumulated snow 

 inland, and its attendant mists, render the soil barren. 



In East Greenland all phanerogamic water plants are absent, 

 because of the long freezing of the water in winter ; in the 

 southern islands there is a Limosella, and a large number of 

 the other Phanerogams seem to take on a special aquatic 

 habit. 



To return to Heard Island. At Corinthian Bay large masses 

 of seaweeds were banked up on the sandy shore. I collected 

 eight species, which have been described by Prof. Dickie.* 

 Amongst them were two new species, and two which occur at 

 Kerguelen's Land, whilst the remainder occur in Fuegia. The 

 main mass appeared considerably different from the masses of 

 algae found on the Kerguelen shore. Diirvilh^a iitilis grew 

 attached to the rocks under the cliffs, but the kelp {Afacrocystis 

 pirifera) does not grow at all about this group of islands, 

 according to the sealers, which is a remarkable fact, in con- 

 sideration of its great abundance at Kerguelen's Land. 



* "Journal of the Linn. Sec ," Vol. XV., p. 73. 



