292 Proceedings of the Club 



L. Britton " On the Flowering Plants collected by Mr. R. S. 

 Williams in the Yukon Territory, 1898-1899." Dr. Britton ex- 

 hibited the plants collected, and by means of a sketch map of the 

 region he compared the diverse floras of the Alaskan region. 



Tuesday Evening, March 13, 1900 



President Brown in the chair ; twenty -six persons were present. 

 v/.The paper of the evening was by Dr. P. A. Rydberg, on the 

 " Phytogeography of Montana/' He divided Montana into three 

 regions, the Great Plains, constituting about one half of the State, 

 and the subalpine and the alpine regions, the last constituting 

 those isolated peaks which exceed 9000 feet. The characteristic 

 plant-coverings of each region, termed formations, were classed 

 under the usual groups as Xerophytic, Mesophytic, Hydrophytic 

 and Halophytic and include, as Xerophytes : 



1. The Buffalo-grass formation, the chief Xerophytic formation 

 of the Great Plains, where high, dry plains are covered with low 

 self-curing grasses giving excellent winter pasture ; including Boute- 

 loua oligostachya, B. /rirsuta, Buchloe dacty hides, and Car ex filifolia. 



2. The Cactus formation, with Opuntia polyacantha, 0. humi- 

 fusa, Cactus viviparus, C Missottriensis, and Lepidium apetalum. 



3. The Sage-brush formation, with Artemisia tridentata, A. 

 cam, A. tripartita, A. arbuscula, together with species of Chryso- 

 t/iamnus, Eurota, and Tetradynia. 



4. Bad-land formation, species of Eriogoniim and Astragalus. 



5. Pine- 



occidentalis. 



Mesooh 



ipulorum and Jump 



The Prairie formation, the most important, forming the grass- 

 lands in the river-valleys, its species belonging to the prairie region, 

 and include species of Agropyron, Elymus, Andropogon and Poa. 



7. The Dog -town formation ; four plants are found in all 



?pala and Munroa 



trifli 



8. The Sand-draw formation, with Cleome trachysperma and 

 species of Euphorbia. In this connection were mentioned the 

 weeds of the region, Heliantlius annuus, Chenopodium album and 

 Avena fatua y all introduced, and Heliantlius petiolaris, Chenopodium 



