JO UNIVERSITY OF MISSOURI STUDIES [192 



timber, and not yet swarded over by pasture grasses, rapidly 

 washes away, leaving extensive patches of naked rock. On the 

 other hand there is a pronounced invasion of light-loving plants, 

 especially composites, whose pappus-surmounted achenes are 

 borne easily by the wind. The first season after underbrushing 

 the herbage is mainly that of the forest floor, in a moribund 

 condition, but with the addition of certain annuals from nearby 

 fields. The fire-weed (Erechthites hieracifolia) is most charac- 

 teristic of the vegetation of such newly deforested tracts. The 

 second season marks the developing of two tendencies: First, 

 the forest strives to spring up again, the oaks especially sprout- 

 ing freely from the stumps of young trees; second, there is an 

 increasing invasion of light-loving plants, consisting of wild 

 prairie plants and of weeds from adjacent fields. The prickly 

 lettuces (Lactuca Scariola and L. virosa) together with the na- 

 tive species of Lactuca, are especially abundant. If the tract is 

 heavily pastured, or suffers severely from fires, the disintegrat- 

 ing forces predominate over the recuperative powers of the na- 

 tive sylvan growth. If the tract is suflfered to grow up again 

 into forest unhindered, the increasing shade of the rapidly ris- 

 ing second growth forest gradually and inevitably repels the in- 

 vaders. 



A brush lot, which is not cleared at once and brought into 

 cultivation, has before it three possibilities: First, it may re- 

 forest itself; second, it may eventually become swarded over, 

 and become a semi-wild pasture, with scattered patches of 

 shrubs, and a few timber trees; third, it may develop into a 

 relatively stable fruticetum. 



The thickets in the vicinity of Columbia are of five main 

 classes : First, recently underbrushed tracts with a sylvan flora 

 in a moribund condition ; second, somewhat older brush lots suf- 



