593] ENGELMAiyN—rA SYNOPSIS OF THE AMERICAN FIRS. I 
A Synopsis of the American Firs (Abies Link.)* 
By Dr. George Engelmann. 
Great confusion prevails in regard to the distinction of species 
of our Firs and in their synonymy. This is owing partly to the 
innate difficulty of the subject and to the very imperfect descrip¬ 
tions in the books, and partly to the inordinate zeal of seed col¬ 
lectors and horticulturists. But in the last decade the western 
mountain regions, the homes of most of o,ur firs, have been more 
fully explored and the geographical limits of the species ascer¬ 
tained ; and in about the same period the anatomical structure of 
their leaves has been investigated, and has furnished welcome aid 
in the distinction and the classification of the species. 
It is a most interesting as well as significant fact that while 
the anatomical structure of the leaves of higher organized plants 
shows considerable uniformity, so that it rarely can be made 
available for diagnostic purposes, the conifers exhibit such a 
wonderful variety of leaf-structure (approaching thereby the low¬ 
est orders of vascular plants), that often a single leaf is sufficient 
•to recognize the genus, and often the species, even when the ordi¬ 
nary characters may leave us in doubt. 
The anatomy of coniferous leaves has been often examined into, 
but the first to appreciate their characters as a means of classifi¬ 
cation was F. Thomas, who in 1865 published an extensive trea¬ 
tise on the subject in Pringsheim’s Jahrb. 4, pp. 23-63. He was 
followed in 18.71 by C. E. Bertrand, Bull. Soc. Bot. France, 
18, pp. 376-81. The same author gave a more elaborate paper 
on this subject in 1874 in Ann. Sci. Nat. Bot. 20, pp. 5-153, with 
12 plates. He was followed in the succeeding year by W. R. Me 
Nab in ‘Proc. Irish Acad. 2, pp. 209-13, with 1 plate ; and in 
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