20 THE TUNDRA AND ITS FAUNA 
whortleberries, &c., again forming an important part of 
the available food supply. Again, as in the case of the 
Swiss alps (p. 74), the vegetative growth of the plants 
is checked by the natural conditions, and thus, though 
stunted in appearance, they are relatively rich in 
proteids and fats, and relatively poor in cellulose, which 
makes their nutritive value high. With all that can 
be said, however, the land offers but little food, and 
the vast majority of the tundra animals depend partly 
or wholly upon the sea, and are therefore necessarily 
confined in their distribution to the margin of the sea. 
The German expedition to Greenland made large 
collections of both birds and mammals, and observed 
the habits of all as closely as possible, and the conclu- 
sion arrived at is that only four of the mammals can 
be said to be permanently dependent upon the land 
for food ; these four being the reindeer, the musk-ox, 
the Arctic hare, and the lemming. Of the many birds 
known to visit Greenland, only two can be said to be 
at once permanent residents and wholly dependent 
upon the land for food. These are the redpoll (Linota 
hornemannt) and the ptarmigan (Lagopus hyperboreus). 
All other birds and mammals are either partially 
migratory or depend to some extent at least upon the 
harvest of the sea. Even of the land plants the last 
statement is partly true, for it is said that the phanero- 
gams are especially abundant about the breeding-places 
of the sea birds, on ground enriched by their droppings, 
and such birds feed in the sea. Again, even of the four 
mammals named, the reindeer, according to Norden- 
skidld, does not disdain seaweed in times of scarcity. 
Everywhere over the globe animals depend ultimately 
upon plants, which alone can fix inorganic matter 
in organic form, but it may be said to be the special 
