526 Part IV. Chapter 3. 
Pedieularis ne Scutellaria galericulata, Polygonum amphibium, P. sagittatum, Salix dis- 
color, S. petiolari 
Cliff Formation. ‚On the banks of the thickly wooded bluffs of the upper 
Mississippi bold rocky ledges arise quite abruptly from the flood plain. The 
lower part of these ledges is sandstone, the upper magnesian limestone. 
Arabis lyrata, Poa compressa a few sedges and lichens occur on the limestone. 
The shaded gullies, however, reaching to the escarpments are tenanted by 
Athyrium filix-foemina, Cystopteris fragilis, Osmunda Claytoniana, Adiantum 
pedatum, Onoclea struthiopteris and Pteris aquilina. The sandstone outcrops 
are moist and occupied in places by Pinus Strobus with ferns. Such ferns as 
Osmunda cinnamomea, O.regalis, O. Claytoniana are at the base of the sand- 
stone. Camptosorus ER occurs on detached limestone blocks on the 
flood plain’). On the rocks of the St. Croix sandstone ledges grow Woodsia 
obtusa, W. ilvensis, Melica mutica, Poa nemoralis, Arabis Iyrata, Campanula 
rotundifoha, Danthonia spicata, Vaccinium pennsylvanicum. 
Of the many plants occuring on the dry ledges in this transition distriet attention may be 
called to Campanula rotundifolia, Danthonia spicata, Eragrostis capillaris, Lechea major (= L. 
villosa), Helianthemum canadense, Erigeron divaricatus, Draba caroliniana, while in shaded woods 
under sandstone ledges are foun ium nivale, Viola pubescens, Isopyrum biternatum, Dicentra 
cucullaria and Anemone nemorosa.. — The moist rocks and sandstone show the presence of 
Aralia racemosa, A. nudicaulis, Camptosorus rhizophylius, Cornus circinata, C. alternifolia, Galium 
aparine, G. boreale, Phryma leptostachya, Rudbeckia hirta, Woodsia obtusa, Cystopteris fragilis, 
Fraguna vesca, Polypodium vulgare, Mitella diphylla, Actaea . Prenanthes (Nabalus) alba, 
Amphicarpaea monoica, Thalictrum Soteiin, and Teucrium canadense. — The open spaces 
on ledges between the forest trees in some places are Be with Cladonia sylvatica, Poly- 
trichum juniperinum, Helianthemum canadense, Lechea major (= L. villosa), Danthonia spicata, 
Eatonia obtusata, Koeleria cristata, Enphorbik corollata, Petalostemon candidus and P. violaceus?). 
B. Prairie- and Sand Hill District. 
a) The true Prairie Territory center. 
The floral covering of the prairies corresponds to their physiography, and 
is essentially homogeneous. In many localities there is noticeable difference 
between the vegetation of low prairies and that of high prairies. The former 
are characterized by a more or less closed type, the latter by the open type 
of formation. The same facies, however, occur in both situations, and the 
change in aspect proceeds entirely from a difference in the secondary species. 
With reference to the constitution of the soil, prairie formations are of two 
kinds. ı. the prairie-grass formation found on loamy soils and 2. the buf- 
falo-grass formation occuring on argillaceous soils, “gumbo” hills and 
plateaux. 
ı) PAmmEL, L. H. and Kıng, CHARLOTTE, M.: Iowa Academy of Science IX (1902); 135- 
2) PAmMmEL, L. H.: Comparative Study of Vegetation, loc. eit 
