Conifers 
birch thickets and alpine plants, and their special ab- 
sorbing Mycorhiza is no doubt well fitted to find the 
necessary salts as rapidly as possible. Under the micro- 
scope the appearance of some pine roots is very re- 
markable, for they are entirely covered over by a sort 
of webbing or felt of fungus threads. 
The distribution of conifer forests in the world is 
particularly interesting. They begin in the north as a 
complete ring surrounding the Pole, but at different 
degrees of latitude. These northern woods are not, 
however, the same. Our Scotch pine goes farthest 
north in Scandinavia, but not in Russian Siberia, where 
it is replaced by the fir, which seems to be able to grow 
better on swampy, peaty ground. Beyond the Urals, 
the Siberian larch is the most northerly tree, and 
sometimes goes as far north as 72° 4o’ N. lat.? 
Pinus cembra replaces the larch from the longitude 
of Werchojansk to Behring Straits. In America, spruce, 
Picea sitchensis, and Pinus contorta and Murrayana are 
the most northern trees in Alaska, but east of the 
Rockies it is the American larch that is the pioneer of 
woodlands, Greenland has not any trees in the present 
geological epoch. 
These differences are very curious and have not been 
explained, but it is possible that the larches can best 
withstand the continental conditions, where there is less 
rainfall, than the pines and spruces. The pine seems 
to prefer drier and rocky ground, and the spruce does 
better on sodden peat and in swamps. 
The “forest primzeval ” of these far northern latitudes 
is not at all impressive. The trees are scraggy, stumpy, 
badly grown and covered with old man’s beard and 
other lichens, 
From these northern forests there are in each con- 
tinent diverging woodlands, which take to the mountains 
when they arrive at more genial latitudes. For, as we 
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