STRUCTURE OF THE FORMATION 85 



itant of the sedge meadow, though not a hydrophyte, is Ver- 

 nonia fasciculata, a plant growing mostly throughout the 

 Carex facies. A few plants of Lycopus americanus, Mentha 

 canadensis, and Scutellaria lateriflora are also scattered 

 through this formation. The taller, overtopping facies ren- 

 der them hardly discernible. All are perennial amphibious 

 plants, by means of suckers or stolons. 



Ratihida pinnata, Lactuca canadensis, Meibomia cana- 

 densis, Heliopsis scabra, Silphium perfoliatum, and As- 

 tragalus carolinianus are typically frequenters of thickets, 

 open woodlands, and grassy banks of streams. With the ex- 

 ception of Lactuca canadensis, which is a dicyclic, all are 

 pleiocyclic herbs. Ratihida pinnata occurs at but a few sta- 

 tions in the prairies near the creek. Under such conditions 

 it hardly ever blossoms and is of no consequence in the forma- 

 tion. A few individuals of Lactuca canadensis are found in 

 the sedge meadow and in low prairies. The wide dissemina- 

 tion of the achenes of the wild lettuce explains its presence. 

 L. canadensis and L. ludoviciana develop rosettes, the leaves 

 of which are mostly killed during the winter months. Mei- 

 bomia canadensis is found near the creek or hedges, where 

 it forms rather dense clumps of individuals. During anthe- 

 sis these clumps are especially prominent on account of the 

 crowded, terminal racemes of purple flowers. Heliopsis 

 scabra occurs at a few stations in the meadows. It has the 

 appearance of a small sunflower. The square stems and 

 connate leaves of Silphium perfoliatum render individuals 

 of this species noticeable in any formation. A few straggling 

 plants of the square-stemmed rosin-weed are found in the 

 meadows. Astragalus carolinianus also grows in meadows. 

 Its large racemes of greenish-white flowers are rendered less 

 noticeable on account of the many other brighter colored 

 forms. Astragalus is one of the first plants to begin growth 

 in the spring, in spite of its late flowering period. 



The remaining six species, Amaranthus torreyi, Convol- 

 lyiilvs sepium, Cassia chamaeci'ista, Lactuca ludoviciana, 



