Dr J. B. Hurlburt on the Forests of North America. 247 
loides), ranges from 37° to 69°. The red current (Ribes 
rubrum), which is found in all the American and Canadian 
forests, Sir John Richardson discovered growing on the 
shores of the Arctic Ocean, within the polar circle. 
Through all this range of latitude, wherever these de- 
ciduous trees are found, these two conditions of climate 
prevail—high summer temperatures and abundant summer 
rains; the cold of winter, with the thermometer even at 
40° below zero, seeming to produce no effect upon such 
plants. 
On the Colour of the Salmon. By Joun Davy, M.D., F.BS., 
London and Edinburgh, &c.* 
All that relates to fish of so much importance as the 
salmon and its allied species naturally excites our interest. 
Amongst the many peculiarities of the genus, when the in- 
dividuals are in their highest condition and best state for 
the table, is their colour—the colour of their muscles gene- 
rally—the well-known salmon colour. No other fish that 
I am aware of, whether in the sea or fresh water, possesses 
this colour, not even those which are associated with it so 
often, and the food of which is very similar. Of fresh- 
water fish, the pike may be mentioned as an example; of 
salt-water, the Perca marina. 
On what does this colour depend ? Commonly I have 
heard it attributed to an oil. The circumstance, that the 
colour is seen only in fish in their highest condition, and 
that in river and brook-trout it is often absent, seem favour- 
able to this opinion, and the more so, as we know that the 
same trout which have pale muscles in streams where there 
is but scanty feed, if removed into ponds or lakes where 
there is abundance of food, whilst they rapidly increase 
there in size, acquire also the peculiar hue distinctive of 
their improved condition. The fact, too, that the salmon 
loses this colour during its lengthened sojourn in fresh 
water after spawning, when it becomes lank and out of con- 
* Read at the Meeting of the British Association for the Advancement of 
Science (Newcastle, 1868). 
