[From BULLETIN OF THE TORREY BoTANICAL CLUB, 44: 431-454. 15 S1917.] 
Phytogeographical notes on the Rocky Mountain Region 
VII. Formations in the Subalpine Zone 
P. A. RYDBERG 
In my Phytogeographical Notes, I have tried to present the dis- 
tribution of the Rocky Mountain phanerogams viewed from three 
different standpoints: (1) their zonal distribution, (2) their geo- 
graphic (provincial) distribution, and (3) their formational ‘dis- 
tribution. In other words, I have classified the plants: (1) ac- 
cording to the life zone to which they belong; (2) according to their 
surface distribution, inside as well as outside the Rocky Mountain 
region; (3) according to the formation to which they belong, i. e., 
whether they are hydrophytes, or mesophytes, or xerophytes, or 
any subdivision of these. When I mention formation this should 
not be taken in a purely ecological sense. In the third paper of 
the series, ‘‘Formations in the Alpine Zone,’’* I indicated that I 
treated the ‘Formations’ purely from a _ phytogeographical 
standpoint, and have nowhere treated plant societies, and still 
two reviewers of my articles (both ecologists) ‘have criticized me 
for not stating which were the characteristic, the most common, 
and the secondary species. To do this, when a whole mountain 
region is treated, is impossible, for in the same class of formations 
certain species may be the characteristic ones in one locality, while 
in another they may be only secondary or even lacking altogether. 
As shown in the fourth and fifth papers of this seriesf the vege- 
tation of the Subalpine Zone consists mostly of forests and grass- 
lands. Especially in the Southern Rockies, where the mountain 
slopes are very steep, another formation is also common, namely, 
the rock-slides. Where the latter do not exist, the slopes are 
mostly covered by forest, while the hog-backs and valleys are 
grasslands. 
A. FORESTS 
As the forests evidently cover the larger area, they may be 
treated first. The forest trees are six: Picea Engelmannit, 
* Bull. Torrey Club 41: 459-474. 1914. 
7 Bull. Torrey Club 42: 11-18; 629-632. I9I5. 
431 
