582 THE FLORA OF THE PRAIRIES. 
wise than an idle whim. With many of the prairie sunflow- 
ers, however, the facts are different; especially is this so in 
the case of H. rigidus. Morning after morning, at flowering 
time, the heads of this species may be seen bending gently 
towards the east; they are erect at mid-day, and at evening 
gracefully droop towards the west. This continues day after 
day for weeks, with surprising regularity and uniformity. 
Later, however, the stems grow rigid and remain nearly ver- 
tical. In this case at least the popular notion referred to 
above seems well founded. 
Aside from the open prairie species already mentioned — 
which embrace the greater part of the most conspicuous ones 
— numerous others of almost equal interest are found grow- 
ing in the low grounds, and in the open forest belts that 
skirt the streams. Prominent among these are coreopses 
aud sunflowers of several species, especially the C. aristosa 
and C. tripteris, Helianthus strumosus, H. decapetalus and 
H. tracheliifolius; the ground nut (Apios tuberosa Moench.) 
with its fragrant, dark purple flowers ; the western iron weed 
( Vernonia fasciculata Miehx.), the great St. John’s-wort 
(Hypericum pyramidatum Ait.), the broad-leaved polygonum 
(P. Pensylvanicum Linn.), and, in more open and drier 
places, the rag-weeds (Ambrosia), the wormwoods (Arte- 
misia), the tick-trefoils (Desmodium), the bush clovers 
(Lespedeza), and the psoraleas. Many species of such east- 
ern plants as love rich moist woods, are also found here. 
One of the strangest features, perbaps, in the flora of the 
prairies, and that which of course constitutes them prairies, 
is the entire absence of arboreal or even suffruticose species, 
the timber of this region, as is well known, forming open 
park-like belts along the streams, which with great propriety 
have received the name of “groves.” Here the species, as 
might be expected, more strongly recall the flora of the East, 
the resemblance extending not only to the trees and shrubs, 
but to the herbaceous species that flourish beneath their 
shelter. But the predominant species can hardly be regarded 
