Prairie Flora 371 



stars of the bluffs are Liatris cylinclricea and Liatris punctata, the lat- 

 ter more common. Liatris scariosa is also frequently found on bluff 

 lands, where Lepachys columnaris is also quite common. Rudbeckia 

 hirta is not very common near the Minnesota river but is found on 

 the Leaf hills. OxyhapUus nyctagineus and Oxybaphus hirsutus are 

 both found on dry banks, the latter more common. Both open their 

 flowers late in the afternoon. Polygonum ramosissimum, Michx, is 

 the name now given to our tall dry-land knot-weed. Heretofore we 

 have called our plants Polygnomum camporum — at least for the most 

 part. Artemisia dracuncuJoides, Pursh is an early autumn plant on 

 dry land. Artemisia caudeta is found on thinner soil, usually near 

 rocks. 



7. The Rock Flora. 



The Minnesota valley, as we have remarked, is crossed in several 

 places by ridges of archaic rocks. Near these rocks and in crevices 

 in them, the conditions are even more xerophytic than on the bluffs. 

 The grass flora of these rocky areas does not differ greatly from that 

 of the bluffs. Bouteloua oUgostachya here reaches a better develop- 

 ment. Indeed this valuable grass seems to be more than maintaining 

 itself, and is becoming an important constituent of dry pastures. 

 Sporobolus brevifolius belongs in the same plant society as the Bou- 

 teloua and is usually found with it. Festuca octoflora is found on 

 thinner soil and ripens its seed in early summer. Agrostis hyemalis 

 is another rock grass, although of course it is found in many other 

 places. Growing in shallow pools on the rocks is a dwarfed form of 

 Alopecurus geniculatus, not more than two decimeters high. It 

 seems to be a distinct variety. Growing among the grasses in these 

 rock areas, Juncus tenuis is quite a common plant. 



Selaginella rupestris is common on the rocks with many interest- 

 ing mosses and lichens. The common fern found in the crevices of 

 these rocks appears to be Woodsia ilvensis. The only other ferns 

 that have been found here are Cystopteris fragilis and Polypodium 

 vulgare, but both of these are quite rare. 



The earliest spring flower in these areas is Lomatium orientale 

 (Coulter & Rose). It blooms in April, sending up its umbel of white 

 flowers from a thick fusiform root stock. Blooming at a time when 

 the prairies are still gray with the last year's grasses, it is a difficult 

 plant to find. Early in May Androsace occidentalis is a very common 

 but rather inconspicuous flowers. Associated with this plant, but 

 not so common is Draba Caroliniana, another very dwarf plant. Grow- 

 ing on the rocks, or where the soil is very thin Draba nemorosa is 

 very common. It is very small in early spring when it commences to 

 bloom, but the plant forks repeatedly and continues to bloom and fruit 

 until it reaches a height of at least three decimeters. Aquilegia cana- 

 densis grows under the shadow of these rocks and is one of the most 

 beautiful spring flowers. Arenaria lateriflora has been found in simi- 

 lar locations. Myosotis virginica is a rather common plant growing 

 in the crevices of the rocks. Oillia linearis, a western plant, is found 

 on the rocks at Cedar lake near Montevideo, tut is not very common. 

 Acerates lanuginosa is another rare plant of these rocky ledges. Per- 

 haps one of the smallest plants to be found among these rocks is 



