175] FLORA OF COLUMBIA AND VICINITY 33 



f. Uliginosae ambrosioides. The ragweed commu- 

 nity, consisting wholly oi Ambrosia trifida, with A.artemisiaefo- 

 lia frequent at the edges, the various plants being bound 

 together often by Polygonum scandens, occupies whole rich flats. 

 No other herbaceous vegetation can compare with this in height, 

 the giant ragweed, Ambrosia trifida, often growing to a height 

 of from eight to fifteen feet. There is a brief vernal vegetation 

 upon these flats, which consists of Ranunculus abortivus, R. 

 septentrionalis, Cerastium nutans, Veronica serpyllifolia and V. 

 peregrina. Certain violets are frequent also, as Viola papilio- 

 nacea, V. scabriuscula, and locally, V. striata. 



II. MESOFHYTES. 



The Mesophytic vegetation coincides with the midlands, 

 the fertile uplands, and such lowlands as have not a hydrophytic 

 flora. It includes six plant-societies : A. The alluvial. B. The 

 sylvan. C. The thicket, or brush flora. D. The flora of the 

 hawthorn glades. E. The flora of bramble and brier thickets. 

 F. The pseudo-prairie flora of wild fields. 



A. Alluviales. Plants of the alluvial zone. 



In the immediate vicinity of Columbia there are but scant 

 traces of the alluvial forest, and there has been no opportunity 

 to study the wooded bottoms of the Missouri. The alluvial veg- 

 etation is intermediate in character between the hydrophytic and 

 mesophytic, having, however, its nearest affinities to the riparian. 

 The soil is very rich, and the vegetation in open places is very 

 rank. The alluvial forest casts a dense shade, and its floor is 

 but scantily covered with shade-loving plants. The herbs are 

 prevailingly urticaceous. When light is let into the forest, a ul- 

 iginose, or low flat, vegetation springs up, but even so the net- 

 tles hold their own well. The alluvial forest has two types of 



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