14 TWELFTH ANNUAL KEPORT. 



The most abundant species of grass found upon the prairies of 

 southwestern Minnesota, are as follows: beard-grass (Andropogon 

 furcatus, Muhl.), commonly here called "blue-joint," Indian grass 

 (Chrysopogon nutans, Benth.), muskit-grass (Bouteloua racemosa, 

 Lagasca), and porcupine grass (Stipa spartea, Trin.), common on 

 land neither very dry nor very moist; another species of beard-grass 

 (Andropogon scoparius, Michx.), and a second muskit-grass (Boute- 

 loua hirsuta, Lagasca), common on dry swells; the fresh-water 

 cord-grass (Spartina cynosuroides, Willd,), in sloughs, making the 

 principal mass of their hay; and rice cut-grass (Leersia oryzoides, 

 Swartz), with the last. The prairies also bear a great variety of 

 flowers, including numerous species of aster, golden-rod, sunflower, 

 blazing-star or button snakeroot, and prairie clover, and the rose, 

 lily, harebell, phlox, gerardia, fringed gentian, and many others. 

 Sometimes the view across miles of the prairie^is made yellow and 

 purple by the multitude of sunflowers, blazing-stars, and gerardias. 



Limits of Species. 



Gradual changes in the flora are observable in crossing the con- 

 tinent either from east to west or from north to south. Many 

 species disappear as the traveler advances, while others, not before 

 present, are met with. A large majority of the plants in the Pacific 

 states are not found east of the Mississippi; and such limitation 

 prevails almost without exceptions between the arctic and tropical 

 zones. The central position of Minnesota therefore makes this a 

 most interesting field for the notation of the limits of species. 



Among our forest trees, the white and red pine, arbor-vitas 

 ("white cedar"), yellow birch, black ash and sugar maple reach 

 their western limit at the east side of the Red river valley. 



No tree of exclusively western range extends east into Minne- 

 sota, and the only shrubs thus noted are Elasagnus argentea (silver- 

 berry), Oenothera albicaulis and Amorpha microphylla; but about 

 fifty herbaceous plants belonging to the flora of the western plains 

 and the Rocky mountains, and not yet known to occur east of the 

 Mississippi river, are found within our limits. These include spe- 

 cies of Ranunculus, Aquilegia, Vesicaria, Linum, Astragalus, Oxy- 

 tropis, Potentilla, Gaura, Peucedanum, Cymopterus, Gutierrezia, 

 Aplopappus, Grindelia, Lepachys, Helianthus, Gaillardia, Senecio, 

 Troximon, Plantago, Pentstemon, Orthocarpus, Echinospermum, 

 Collomia, Gentiana, Asclepias, Suaeda, Comandra, Euphorbia, Alli- 

 um, Carex, Sporobolus, Aristida, Buchloe, Elymus, and Beck- 

 mannia. 



