74 



smaller ones of Andropogon scopariiis, Paniciim virgatiim, Lcptoloma 

 cognatiun, and some Paspalum setaceuni. Other less important spe- 

 cies of bunch-grasses are Stipa spartea, Cypcnis Sclnvcinitzii, Pani- 

 citui pscitdopubcscois, and Kocleria cristata, indicating a former lux- 

 uriant development of the consocies. There are also scattered plants 

 of Froelichia floridana, Monarda punctata, Liatris scariosa, Lith- 

 ospermnm Gmclini, Tephrosia rirginiaiia, and AniorpJia cancsccns. 



The aspect of the mixed consocies varies considerably from one 

 area to another, but a few plants may be mentioned which are usu- 

 ally common and conspicuous. In the vernal aspect Viola pcdata, 

 Pentsteinon hirsiitiis, and Lithospennurn Gmclini are in bloom. They 

 are followed during the aestival aspect of July by Tradcscaniia rctlcxa, 

 Chrysopsis villosa, Oenothera rJwinbipctala, and Amorpha cancsccns. 

 In the serotinal aspect Solidago nemoralis, Liatris scariosa, and a 

 number of other composites appear. The consocies was not under 

 observation during other aspects. 



Cultural Changes 



The railroads which traverse the sand areas make apparently 

 little effort to keep the right of way free from tall grasses or other 

 plants, and as a result fires occur frequently. Their chief effect seems 

 to be to limit the growth of bunch-giasses to the largest species, and 

 of those only the larger bunches are spared. The deposit of cinders 

 along the track is also an important factor in the vegetation. It tends 

 to increase the intensity of the xerophytic conditions, and hence to 

 limit the plant growth. In this the greater heat absorption of the 

 dark-colored, cindered surface may be controlling for the perennials, 

 while the poorer chance of seed planting may tend to reduce the num- 

 ber of the annuals. The general effect of both fires and cinders is to 

 increase greatly the amount of open space and to restrict the vegeta- 

 tion mainly to a few of the hardier species. There are of course fre- 

 quent scattered relics of many other species of the association. An 

 association of quite similar appearance, characterized by Andropogon 

 scoparius and Petalostcniuni purpurcuni, appears on some of the 

 gravelly ridges along Lake Michigan, where the surface of the 

 ground is covered with flat rounded pebbles one to two inches (2-5 

 cm.) in diameter. 



North of Oquawka, along the Chicago, Burlington and Quincy 

 railroad there are many huge bunches of Sorghastruni nutans, An- 

 dropogon furcatus, and Andropogon scoparius, separated by inter- 

 spaces 3-15 feet (1-5 m.) wide. Nearly all these bunches are dead in 



