TRANS. ST. LOtfIS ACAD. SCIENCE. 
[594 
1877 the same published an exhaustive paper in the same jour¬ 
nal, pp. 673-704, with 4 plates. E. Purkinje, of the Foresters’ 
Academy of Weisswasser in Austria, made, four or five years 
ago, extensive investigations on the same subject, but has, I be¬ 
lieve, not jet given his results to the public. My own studies in 
this line, commenced some fifteen years ago, when the conifers 
of the Rocky Mountains first got into the hands of botanists, have 
been carried on more assiduously within the last three years. 
Highly important as the microscopic investigations of the leaf 
anatomy are, they have sometimes been relied on too exclusively, 
disregarding the characters furnished by the reproductive organs.* 
It may not be useless to repeat that the leaves of all firs are 
sessile with a circular base (leaving a circular scar in falling oft), 
and without the prominent persistent ligneous cushion which is 
peculiar to the spruces. They are usually more or less flattened, 
grooved above and keeled below, and those of the branches are 
mostly twisted above the base so as to give them a more or less 
distichous direction ; the leaves of the erect shoots are thicker and 
convex above, and not twisted. The tip of the leaves of young 
trees and of the lower branches of older ones is notched in almost 
all species ; the leaves of robust shoots and of fertile branches are 
mostly entire, obtuse in some, acute in others.! All the leaves 
have stomata on the under side, arranged in a smaller or larger 
number of series, forming bands on each side of the keel. On 
the upper side of the leaf stomata are present in some, especially 
in those with thicker leaves, and absent in other species, mostly 
in those with flatter leaves ; in several species the leaves of the 
lower or sterile branches are without stomata above, and the 
thicker ones of the upper or fertile branches have a few (in the 
upper part of the groove) or many. The thick epidermis of the 
upper surface is mostly underlaid and strengthened by very ro¬ 
bust longitudinal cells, with thick walls and a very slender cavity, 
* The separation by Bertrand, followed by McNab, of Abies nobilis from the other firs, 
and the connecting it with Pseudotsuga Douglasii, notwithstanding their striking differ- 
gation. 
f Hence the necessity of collecting, if possible, branches of a young tree, erect shoots, 
lower branches of older, fertile trees (the only specimens which we usually find in herbaria . 
