33 2 
A. G. Tansley. 
Rndbeckia hirta, Lepachys pinnata, Heliantlius stmmosus, etc., etc. 
Among these are Silphium laciniatum (the well-known compass- 
plant), S.terebinthinacenm (prairie-dock), S.integrifolinni (rosin-weed) 
and Cacalia tuberosci (Indian plantain) with their stiff conspicuous 
leaves. Other common high prairie species are Potentilla 
canadensis , the beautiful Phlox pilosa and glaberrima, Petalosteinum 
purpureum and candidum (prairie clovers) and Lobelia spicata. 
The prairies show several seasonal phases marked by the 
showy flowers of different abundant species which mature at 
different periods of the summer and early autumn. 
The Chicago prairie is certainly a relatively stable plant- 
community, and some local botanists declare that its edges have 
shown no tendency to be invaded by forest for the last half-century. 
Professor Cowles, however, considers that on the whole it is 
probably to be regarded as a stage antecedent to forest. The 
Chicago region is physiographically very young, the low-lying land 
near the city and to the south-east having been comparatively 
recently exposed by the retirement of “ Lake Chicago,” the more 
extensive predecessor of Lake Michigan : and on general grounds 
it may well be that the succession of vegetation over the region as 
a whole has not yet reached its “ climax type.” In some places 
marsh or fen passes not into prairie but directly into forest. The 
factors which determine these different fates are not certain, but it 
is quite likely that they are due to the historical accident of the 
invasion of forest vegetation in one place and prairie vegetation in 
another, according to local proximity of the two parent types. 
When the prairie vegetation obtains a good hold of the ground, 
it would naturally greatly delay, even if it did not wholly prevent 
the invasion of forest. 
Start for the West. 
Taking leave of our kind hosts of Chicago, we left the city 
westward bound on the evening of Friday, August 8th, travelling 
straight through to Lincoln, Nebraska, where we arrived on the 
following morning. Through Illinois the characteristic oak-woods of 
the rising ground, largely dominated by Quercus inacrocarpa, alternate 
with prairie in the depressions with black soil often derived from fen. 
The plain, however, is largely cultivated (maize, wheat, etc.) and 
the woods are mostly passing into a degenerate condition owing to 
their use as pasture grounds for cattle. The Mississippi was 
crossed after nightfall, and throughout the night we traversed the 
state of Iowa, a typical prairie state, now almost entirely under 
