THE NEBRASKA SAND HILLS. 279 



That Sand Hill vegetation has been very successful in meeting these 

 ■conditions is fully attested by a glance at the region as we find it to- 

 day and a comparison with the dismal waste of bare sand dunes that 

 once wandered over this same area. 



Aside from the bunch-grasses, the most characteristic plant of the 

 uplands is the soap weed or dagger weed (Yucca glauca) which often oc- 

 curs in great abundance on the upper slopes. In certain portions of the 

 region over restricted areas this species really becomes dominant and 

 the bunch-grasses then play only a subordinate part in the floral cover- 

 ing. The dagger weed reaches its best development on the south and 

 west exposures, although it is by no means confined to these slopes. 

 The sand is often blown away from the roots for many inches beneath 

 the rosette of bristling leaves, and yet the plant continues to thrive. 

 Frequently it puts out new shoots from the exposed roots and develops 

 new rosettes of leaves beneath the old. 



The so-called "cat steps" formed on steep slopes in the Sand Hills 

 owe their origin to the grazing habits of cattle and very frequently to 

 the presence of dagger weeds. On such slopes the cattle, avoiding the 

 sharp-pointed leaves of the Yucca, follow angling paths which eventually 

 become netted and worn into the sand in such a way as to cover the 

 hillside with a network of trails. Clumps of dagger weed often fill in 

 the more or less diamond shaped meshes of this network. From a dis- 

 tance, such a slope bears a close resemblance to the "cat steps" so com- 

 monly seen on steep slopes in the loess region. The origin is, however, 

 very different. One may find in the Sand Hills a great many stages in 

 the development of these netted trails. They are not necessarily always 

 associated with the dagger weed, since they also occur on slopes with 

 bunch-grasses only. 



Like the little blue steam, the dagger weed has little value in the 

 region aside from its interesting and important role in the life history 

 of the I'idges and slopes. Some economic value is attached to it in that 

 it is eaten by cattle to a slight degree. Especially when the plant is in 

 bloom, if the range is rather short, stock frequently strip every juicy 

 flower from the large spike or panicle, sometimes even eating the axis 

 well down among the needle-tipped leaves. I have seen them attack 

 the young capsules when the range is especially short, so that in a 

 closely grazed pasture one seldom flnds a single fruit of the species. 



Beside the bunch-grasses and the dagger weed there are many other 

 species that occur in greater or lesser frequency in the bunch-grass as- 

 sociation. The hairlike eragrostis (Eragrostis trichodes) is an important 

 secondary grass of the uplands that frequently shows the bunch-grass 

 habit. So also Indian millet (Oryzopsis cuspidata), and the black grama 

 grass' (Bouteloua hirsuta) are quite commonly seen in the intervals be- 

 tween the bunch-grasses. In fact there are more than one hundred 

 species of grasses alone in the Sand Hills, many of which are conflned 

 to the uplands. Besides the species already mentioned the following 

 are other common associates of the bunch-grasses; Annual eriogonum 



