1 6 UNIVERSITY OF MISSOURI STUDIES [158 



of water-plants; II. The mesophytic, consisting of plants grow- 

 ing in soil neither excessively moist nor dry ; III. The xerophy- 

 tic, consisting of dry-soil plants. To these two other classes 

 are to be added; IV. The parasitic and saprophytic higher 

 plants; and V. The anthropophytic plants, consisting of those 

 cultivated and the weeds that accompany human activity. 



I. HYDKOPHYTES. 



The hydrophytic flora is not strictly a unit, but includes 

 several distinct societies. These in the main are composed of 

 plants that need water in abundance, but a natural classification 

 based on the factor of water alone will not hold. It is well 

 known that shore-plants are xerophytic rather than hydrophytic, 

 yet treating the lowland flora as a whole, the littoral vegetation, 

 at all times very near the limose and the amphibious, cannot 

 well be separated. And so the riparian vegetation, while hy- 

 drophytic as to its trees and shrubs, often includes a considerable 

 number of mesophytic herbs. A willow on a clay bank has roots 

 long enough to reach the water of the stream, while the herbs 

 under its shade may be of mesophytic types. The riparian flora, 

 like the littoral, while extremely natural in itself, cannot in ex- 

 actness be reckoned as a wholly hydrophytic flora, though it 

 forms a prominent part of the lowland vegetation. The hydro- 

 phytic province embraces, then, all waters, swamps, swales and 

 marshes, and the shores and low banks of streams. The wooded 

 bottom lands, however, are more naturally treated as the lowland 

 portion of the great mesophytic forest. The fontinal flora of 

 moist limestone banks and of dripping rocks is similarly to be 

 treated as a part of the rupestrine vegetation. 



The hydrophytic flora may most conveniently be divided 

 into four zones: A. The aquatic; B. The marginal; C. The 



