PAPERS ON BOTANY 125 
or edge of the upland, shown by the line of short hachures. 
Forest had at one time spread about a quarter-mile from this 
edge, and had since been cleared for cultivation. New forest 
growth near the edge has come in since about 1911. Prairie 
and forest herbs occur in mixture in open spaces between sap- 
lings. The largest prairie patch has almost luxuriant vegeta- 
tion, in which grasses, and Parthenium integrifolium, and the 
conetlower Brauneria purpurea, are conspicuous. There are 
also a few long-lived perennials, such as Silphium terebin- 
thinaceum (Fig. 2), which are commonly absent from prairie 
that has not been established for many years. The invasion of 
forest seems to be upward, because the shade falls on the part 
of the slope just above the position of the trees. The boundary 
between prairie and forest vegetation is in places somewhat 
ragged and indefinite, partly because prairie and forest herbs 
intermingle along the border, where also occur the forest- 
border sunflowers, Helianthus strumosus and H. divaricatus 
(Fig. 3), and the bushy legume Baptisia leucantha, and the 
half-shrub Ceanothus americanus. The badly washed spur at 
the right in the map is mostly bare clay with scattered bunches 
of Andropogon scoparius, and a few interstitial annuals, in- 
cluding two small species of Lespedeza, which are typical in 
new growths of clay hillsides. The taller bunch-grass Andro- 
pogon furcatus is common in places (Fig. 4). A long, narrow 
spur-top just east of the area mapped is covered with prairie 
of apparently recent development from forest. 
Small prairie patches in the woods are common also along 
the Embarras river, especially on the south-facing flanks of 
spurs, on both sides of the stream. Figures 3 and 4 illustrate 
two of these patches. One extensive south-facing hillside, once 
forested, is now part of a large pasture. Many kinds of prairie 
plants persist on this hillside, due to the topographically 
determined dyness and instability of soil, which keep the blue- 
grass from driving out the native plants, as it does in level or in 
well-watered pasture. 
In conclusion, it appears that these small enclaves or open- 
ings of prairie in forest must be of fairly general occurrence, 
that they deserve to be generally known, and some of them set 
aside as natural history preserves. They illustrate admirably 
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