THE PRAIRIES. 15 



and there are scarcely any absorbing laterals in the first 2 or 3 feet of soil. 

 In the deeper soil they branch irregularly but not very repeatedly, many of 

 the roots reaching the water-level at about 80 inches. It is probable that in 

 drier soil they would penetrate deeper. The smaller roots near the tips (1 or 

 2 feet of the extremities) often form brownish, hairlike branches which may 

 run 12 to 18 inches without giving off laterals or, on the other hand, may be 

 profusely supplied with small branches. Not infrequently the root-ends 

 break up into two or three pieces, all of which are supplied with laterals. In 

 general the extremities are covered with fine, short branches which extended 

 to the water-level. 



THE SUBCLIMAX PRAIRIE. 



During the last week in March of 1918, a number of root systems 

 were studied near Peru, Nebraska, at a station about 60 miles south- 

 east of Lincoln. The prairies in this region are very similar in floristic 

 composition to those near Lincoln, as has been shown by the studies 

 of Thornber (1901) and others. Root systems of a number of species 

 were studied in a prairie area covering the exposed southeast slope of a 

 loess hill. A number of list quadrats which were made during the 

 preceding summer revealed the dominance of Andropogon furcatus 

 and A. scoparius. Indeed, the striking feature of the vegetation is the 

 luxuriant growth of these bluestems. Andropogon furcatus extends to 

 the very crest of the ridge. Here the stems reach heights of 5.5 feet, 

 while the roots penetrate the mellow loess soil to a maximum depth of 

 9 feet 3 inches. This root penetration exceeds by 2 feet the maximum 

 depth recorded for any plant of this species in clay-loam soil. 



As pointed out by Clements, this type of prairie, lying in a region 

 of somewhat higher rainfall, is probably subclimax. The luxuriant 

 growth of Andropogon upon the high ridges indicates conditions very 

 favorable for chaparral growth and (as indicated later) thickets of 

 Corylus, Rhus, and Symphoricarpos are very frequent in this grass- 

 land. It is not uncommon also to find seedUngs of elm and oak near 

 the edges of these thickets. Indeed, except for fires, grazing, or other 

 disturbances, much of this grassland area would probably become 

 chaparral and forest. 



Other species examined near the hilltop were Brauneria pallida 

 and Lygodesmia juncea. Near the foot of the slope, and where an 

 abundance of clay makes the soil much harder and more compact, 

 specimens of Lespedeza capitata, Amorpha canescens, and Ceanothus 

 ovatus were excavated. 



Brauneria pallida. — As is frequently the case in eastern Nebraska prairies, 

 this perennial herb, while never abundant, occurs in such numbers as to be a 

 conspicuous component of the prairie flora. Two plants were examined. 

 The smaller had a tap-root 5 mm. in diameter and reached a depth of 5.5 

 feet; the larger, with a diameter of 11 mm., reached a depth of 8 feet. The 

 strong tap pursues a vertically downward course, tapering very slowly. While 

 the older parts (the first 2 to 5 feet) are more or less woody and chocolate- 



