594 TRANS. ST. LOUIS ACAD. SCIENCE. 



1S77 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 yet 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. f 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- 

 ences in pollen, fruit, and seed, must be considered as the result of such one-sided investi- 

 gation. 



t 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 

 because easily attainable) and branches with male and such with female flowers, or with 

 their vestiges; besides these, the cones and seeds and young seedling plants are important 

 A slice of the bark of old and of young trees ought to complete the material. 



