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17G MISSOURI BOTANICAL GARDEN, 



at which time the Drairics gradually assume their winter 



aspect. 



Thickets. 



Bordering the prairie and forming a transition between it 

 and the deciduous oak forest^ one finds an accumulation of 

 shrubs of greater and lesser heights, causing the one to grade 

 into the other. This thicket is fringed with low growing 

 shrubs such as the early flowering Rhus canadensis, Ribes 

 gracile and Syniphoricarpus vulgaris, t 



brilliant 



landscap 



and 



be 



»tably 



glabra and Sambucus canadensis, with which, in different 

 locahtieS; Euonymus atro purpureas, Cercis canadensis, Rham- 

 mis lanceolata, Pynis coronaria and C omits asperi folia are 

 associated in greater or smaller numbers, one of the species 

 usually being subdominant. On the plateau at Jefferson 

 Barracks, south of the buildings, Primus Persica in places 

 forms extensive thickets. The undergrowth is composed 

 of various shrubby Rosaceae, notably Rosa arkansana and 

 R, blanda, R, humilis being less frequent, Rubus canadensis, 

 together with Rubus ocddentalis and R, villosus. Grape 

 vines, Vitis riparia, as well as Celastrus scandens, Mcnisper- 

 mum canadense and Smilax ecirrhata, S, herbacea and S, hispida 

 twine through the bushes as does, in the latter part of the 

 year, Polygonum dumetorum scandens. Rhus Toxicodendron 

 in places is abundant. This happens especially where the 

 outer fringe of the thicket is composed almost exclusively of 

 Rubus canadensis, which in late summer and fall is sometimes 

 complet(^ly hidden by the poison oak. The forest trees 

 which border the prairie are chiefly Quercus alba, Q. coccinea 

 tinctoria and Q. Muhlenbergii, an occasional large specimen 

 of Plaianus ocddentalis being found. Queixus stellata is 



frequent here. 



Between the outer fringe of Symphoricarpus vulgaris and 

 the prairie proper lies a narrow zone^ encroaching upon both, 

 and occupied by herbaceous plants. In the earlier portion of 

 the year Claytonia virginica, Viola palmata and F. palmata 



