1886. | BOTANICAL GAZETTE. 57 
In 1865 F. Thomas, in Pringsheim’s Jahrbucher, iv. pp. 23-63, 
first called attention to these leaf characters as means of classifi- 
cation. The other authors upon this subject have been C. E. 
Bertrand, Bull. Soe, Bot. France, xviii. pp. 376-381, 1871, and 
Ann. Sci. Nat. Bot., xx. pp. 5-153, 1874; W. R. McNab, Proc. 
Irish Acad., ii. pp. 209-218, 1875, and in the same journal, pp. 
673-704, 1877; E. Purkinje, of Austria, has also made studies, 
but his results have not been learned. Probably the most dili- 
gent and successful investigator of this subject was the late Dr. 
Geo. Engelmann, whose name in connection with this group of 
plants is the most familiar in this country. me of his conclu- 
sions have been published in his “Synopsis of American Firs,” 
published in 1878 in the Trans. St. Louis Acad., iii. pp. 593-602, 
and particularly in his “ Revision of the genus Pinus,” published 
in 1880 in the same journal, iy. pp. 161-189. It is upon this last 
contribution that the work recorded in the present paper was 
based. Dr. Engelmann made use of the characters obtained from 
leaf-structure to define many of his subdivisions of the genus, but 
did not carry them on into the species. Our object has been, in 
the first place, to verify his work; in the second, to make use of 
these characters in the discrimination of species 
fossil botany in the de- 
In several cases it will 
also be noted these characters serve to separate forms which have 
been doubtfully placed together, and more frequently to bring to- 
gether certain forms which have been kept apart as doubtful 
Species, 
It will be observed that Dr. Engelmann’s arrangement, in the 
main, has been confirmed, trifling modifications here and there 
being made to better express what is conceived to be true rela- 
tionships. The necessity of a lineal arrangement, of course, dis- 
torts many of the facts, but we believe it to be the most natural 
yet suggested. 
