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Art. XIII. — Onthe Physical Disl7ihution qftheComv'E.w^ and 
their affinity with the Ephedrace^e; with observations on the 
utility of the Barh of the Larch in the pi^ocess of tanning 
Leather. By John Yule, M.D. E.R. S. Edin. and M. W. S. 
Communicated by the Author. 
Of the Tribes of plants forming so many kindred groups, scat- 
tered over the surface of the earth, the Conifer^e afford many 
remarkable instances. The whole of these agree in certain leading 
characters, but frequently differ in other strongly marked shades, 
which it is the object of the naturalist to trace and delineate, as 
not unfrequently indicating the purposes to which they are 
capable of being applied in the various useful arts. That ana^ 
logy, in this respect, forms of itself an uncertain guide, is readi- 
ly admitted; yet the hints thus acquired frequently shorten our 
inquiries, by immediately directing us towards the more cer- 
tain tests of chemistry. 
Whilst some of these tribes are found approaching the line 
of perpetual snow, on the shoulders of mountains, within the 
arctic circle, others, more tolerant of the sun’s rays, inhabit 
the mountains and more elevated plains of the tropics On 
the mountains of Mexico, Humboldt and Bonpland invariably 
found the true pines possessing the extreme limit of arborescent 
plants ; and Wahlenberg and Von Buch unite in describing trees 
of the same tribe occupying nearly similar stations on Mont 
Blanc and Mont Perdu (Lat. 42° 46'), and on Solitelma in 
Lapland (Lat. 68° north.) 
In these last instances, the pines were found approaching 
nearer the line of perpetual snow than the firs or spruces, which 
disappeared about 400 feet lower, at the medium temperature 
of 37J° Fahr. *f* , the Pines extending to within 2800 feet of 
* Humboldt and Robert Brown, to whose accurate and extensive observations 
we owe so much, note a remarkable fact with respect to the physical distribution 
of these tribes, — -that those of the southern differ from those of the northern he- 
misphere, on which none of the Podocarpi, Dacrydii, and Araucariae, See. have 
hitherto been detected. 
+ Wahlenberg. — Linneeus* Tour in Lapland. — Humboldt, Geograph. Plant.— 
Mich. Arbres Forest. 
S 
