ENGELMANN A SYNOPSIS OF THE AMERICAN FIRS. 593 



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 our 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 1S65 published an extensive trea- 

 tise on the subject in Pringsheim's Jahrb. 4, pp. 23-63. He was 

 followed in 1S71 by C. E. Bertrand, Bull. Soc. Bot. France, 

 18, pp. 376-S1. 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. Mc 

 Nab in Proc. Irish Acad. 2, pp. 209-13, with 1 plate ; and in 



* I follow Link {Linnaa, 15, 525, 1S41) in his name, definition, and circumscription of 

 the Genus, which seems 10 be a very natural one, comprising the silver or balsam firs. The 

 synonym Picca Don. in Loudon Arb. 4, 2329, 1S3S. is the older name and enjoys the Lin- 

 nean prestige, but is contrary to classical (Plinius, etc.) and philological authority. The 

 name Abies is generally adopted on the continent of Europe, while Picea was heretofore 

 principally used in England, but is now being abandoned. Pica Link (the same as Abies 

 Don) is the proper name for the spruces. Tournefort, the elder DeCandolle, Gray, and 

 others, comprise under the name of Abies both firs and spruces. The generic distinctions 

 between them are based both on the floral and fruit characters as well as on the leaf 

 anatomy. 



hi 3S [Jan. 10, 1S78.] 



