ECOLOGICAL CROSS-SECTION OF BOULDER PARK 283 



In summing up the lists of characteristic plants from the various 

 stations, we find that there are forty-nine species represented and that 

 but few of these have a large distribution. Artemisia canadensis 

 grows at five stations which cover all of the directly exposed places. 

 Calochortus gunnisonii is found at two points which differ greatly 

 in light intensity and soil moisture, showing that it can exist in a 

 wide range of conditions. The conditions at Station No. 10, the 

 sagebrush ridge, are rather extreme, but nearly all the plants which 

 make up its flora are represented elsewhere, often in a very different 

 habitat. Thermopsis divaricarpa grows only in the most shaded 

 places. Juncus balticus, though present at a number ot stations, 

 is limited to dry grassland. Campanula petiolata is able to grow 

 and flourish almost anywhere. It exists even in the extreme condi- 

 tions of the sagebrush ridge at the north of the park. Aragallus 

 lambertii grows at all of the dry, warm stations, while the other repre- 

 sentative of the genus, Aragallus richardsonii, is much less widely 

 distributed, although it has probably had the same opportunities 

 of invasion. Achillaea lanulosa is the only other species which is 

 abundant at more than two stations and it shows a tendency to 

 grow under very varied conditions. 



The discussion of each species in relation to its habitat would be 

 rather beyond the range of this article. 



A comparison of the individual stations shows, as would be 

 expected, great similarities in the dry grassland areas and considerable 

 likeness in the subsidiary plants of the two lodgepole-pine stations. 

 The willow scrub, with its humus soil and high water content, has 

 naturally a flora very different from the other stations. 



As noted at the beginning of the paper, the stations were selected 

 to give typical conditions. Some of the plants which are prominent 

 in one locality may be present, though in small numbers, in another 

 place. These are recorded only from the station where abundant. 

 The following lists bring together the species which have been taken 

 as representative of the flora of the different stations. Figures follow- 

 ing the names are the station numbers. 



