52 UNIVERSITY OF MISSOURI STUDIES [194 



similar clumps. Again rich slopes may support a dense growth 

 of hazel (Corylus Americana). The herbs also are of hetero- 

 geneous types. Along the rocky beds of ravines occur patches 

 of Viola Raiinesquii, Draba cimeifolia, Plantago Virginica, and 

 CerasHum nutans. Allium Canadense and Nothoscordiim 

 striatum are also common along such beds. Later in the season 

 Rudheckia triloba is the commonest herb. On the hill-slopes 

 Hybanthus concolor, Verbena Aubletia, Taenidia integerrima, 

 Camassia Fraseri, Astragalus Mexicanus, and Corydalis flavula 

 are conspicuous in spring and early summer, to be followed later 

 by Asclepias verticillata, Ruellia ciliosa, R. strepens, Koellia 

 Virginica, Monarda Ustulosa, Heliopsis scabra, Rudbeckia spp., 

 Silphium integrifolium, and Helianthus hirsutus. Hill summits 

 are swarded over with various panic-grasses (Panicum spp.), 

 and Danthonia spicata. Viola pedata, Comandra imtbellata, Par- 

 thenium integrifolium, Zisia cordata, and the bush-clovers, Les- 

 pedeza spp., are characteristic herbs. Andropogon furcatus, A. 

 avenaceus, and Triodia cuprea are common late grasses. 



D. Spinosae. The flora of the hawthorn glades, 



a. Spinosae mespileoides. The haw association. On 



the coal measures to the north of Columbia occur ex- 

 tensive tracts of thorny thickets interspersed with timber trees 

 of a lowland type. These tracts appear to stand for former 

 prairies, since on the limestone in the sylva proper such chaparral 

 growths do not occur, though small patches of haw (Mespilus) 

 are frequent, especially along the roads and on the summits of 

 cliffs. Together with the species of haw (Mespilus) grow the 

 similar wild crab-apples (Pyrus lowensis and P. angustifolia) , 

 the wild plums {Primus hortulana and P. Americana) , the black 



