44 UNIVERSITY OF MISSOURI STUDIES [l86 



D. paniculatum S. serotina 



D. viridiflorum S. Canadensis 



D. Dillenii Aster cordifolius 



D. rigidum A. Drummondii 



Amphicarpa monoica A. sagittifolius 



A. Pitcheri Helianthus hirsutus 



Agastache nepetoides H. strumosus 



Gerardia grandiflora Prenanthes altissimum 



Phryma Leptostachya Hieracium scabrum 

 Solidago ulmifolia 



The primary grouping of the plants of the sylva depends 

 mainly upon the soil and the physiographic position. A sec- 

 ondary grouping can often be made out according to the season 

 of the year, though obviously this is possible only in the case 

 of herbs. In the limestone district four physiographic plant- 

 groups are discernible, i. The ravine group, consisting of a 

 slender thread of riparian plants along the stream in the center 

 of the ravine, and where there are out-croppings of rock, certain 

 rupestrine species commonly occur. In general the flora of ra- 

 vines consists of such plants as demand rich soil and considerable 

 moisture. 2. The hillside-group, consisting of plants requiring 

 a rich soil but less water than the foregoing; it is tolerant of 

 more light, but here, too, there are out-croppings of rock and 

 rupestrine forms. 3. The hill-summit group, consisting of 

 plants habituated to a dry, often stony, semi-barren soil, and 

 forming a transition to the xerophytic flora. 4. The plain- 

 group, consisting of strictly mesophytic plants growing under 

 conditions of soil, moisture and light that may be considered 

 normal for the sylva. Riparian and rupestrine elements are 

 seldom noticeable. The forest-plain is now very poorly pre- 

 served, most of it having been cleared into farms or transformed 

 into permanent pastures. 



