scattered individuals here and there, or may occasionally form rather dense communities; spiderwort (Tradescantia virginica), tufted hymenopappus (Hymenopappus filifolius), purple blazing star (Lacinaria squarrosa), lance-leaved psoralea (Psoralea lanceolata), western thistle (Carduus plattensis), rough sunflower (Helianthus scaberrimus), prickly poppy (Argemone intermedia), long-leaved milk vetch (Phaca longifolia), green milkweed (Acerates viridiflora), switch grass (Panicum virgatum), prairie pink (Lygodesmia juncea), Geyer's spunge (Euphorbia geyeri), yellow evening primrose (Œnothera romhipetala), sweet pea (Lathyrus ornatus), and hairy golden aster (Chrysopsis villosa). All of these plants occur as scattered individuals except the milk vetch and prairie pink, which are often gregarious. They all show striking anatomical characters that doubtless aid in their survival in such dry soils, exposed to such trying climatic conditions.
In addition to the grasses and the common herbaceous associates the vegetation of the upland is rich in species of low shrubs. In many restricted localities these under-shrubs compose the bulk of the vegetation and really rival the bunch-grasses in dominance. Among these low, much branched, woody plants, New Jersey tea (Ceanothus ovatus), Bessey's sand cherry (Prunus Besseyi), poison ivy (Rhus radicans), and the prairie clovers (Kuhnistera purpurea, K. villosa, and K. alba) are the commonest and most widely distributed. All of these plants are dwarfed, much branched shrubs often growing in communities. 'New Jersey tea is found most frequently near the tops of the hills on north facing slopes, where the dense, light
