54 UNIVERSITY OF MISSOURI STUDIES [19^ 



F. Agrestes. Plants of wild, or semi-wild, fields. 



There are two types of wild fields: First, park-like tracts 

 with frequent trees left standing for shade or for their nuts, 

 fruit, or timber; second, wild open permanent pastures. Both 

 forms have an herbaceous flora that is essentially prairie, but with 

 many ruderal plants. The study of the invasion of these prairie 

 plants is interesting. While in the immediate vicinity of Co- 

 lumbia there are now no prairies proper, it seems probable that 

 at no very distant time the region of the coal-measures was 

 prairie. It has been seen that the sylva there has been derived 

 from the timber accompanying the streams, and that such trees 

 as Quercus macrocarpa, Q. platanoides, and Q. palustris, are 

 dominant. It has also been seen that the hawthorn glades stand 

 probably for former prairies. Moreover at the summits of the 

 cliffs there is commonly a narrow zone of typical prairie species, 

 and similar patches occur on the summits of certain hills. In 

 open thickets and in old roads in woods little remnants of prairie 

 vegetation still persist. It is easy then to understand the source 

 of the steady invasion of prairie species. 



a. Agrestes caryoides. The hickory association of 

 trees in park-like fields is due primarily to human selection. 

 When the forest was felled, certain trees, notably the various 

 hickories (Carya spp.), the walnut (Juglans nigra), the per- 

 simmon (Diospyros Virginiana), the honey locust (Gleditschia 

 triacanthos) , the Kentucky coffee tree {Gymnocladus dioica), 

 and various oaks and ashes (spp. of Quercus and Fraxinus), 

 were left standing for various economic reasons. The herbs are 

 essentially the same as that usual to the open wild fields, the 

 sward consisting of Poa pratensis, or often of cultural species, 

 such as the meadow grasses and clovers. The spring beauty 

 (Claytonia Virginica) is very common in spring. 



