63 



the consocies. No record was made concerning; the abundance of 

 each species. 



Bouteloua hivsuta, Ritellia ciliosa, Ambrosia psilostachya, and 

 Runiex AcctoscUa appear as the most frequent of the secondary 

 species, while Lcptolovia cognatum naturally appears in every quad- 

 rat. The average number of species in each quadrat is 10.6, while the 

 whole number observed in the Oquawka area is 47. 



The consocies was not under observation during the vernal sea- 

 son, but Baptism bracfcata and Dclphiniuiii Penardi are probably 

 quite conspicuous at that time. During the aestival aspect of late 

 June and July Oenothera rhoinhipetala and Aniorpha cancscens are 

 much in evidence. These are followed in August by Monarda punc- 

 tata, and the red spikelets of Lcptolonia cognatum are also veiy 

 conspicuous at that season. In the Hanover area the vernal aspect 

 is characterized by Pentstemon hirsutus, wdiile the aestival and sero- 

 tinal conditions are essentially the same as at Oquawka. 



In the Oquawka area contact between this consocies and others 

 was not observed. At Hanover it grades into the mixed consocies 

 next to be described. There is no sharp line between the two, but 

 other species of grasses appear, the spaces between the bunches become 

 wider, and a greater number of secondary species occupy the bare 

 sand thus available. 



The Mixed Consocies 



In the Hanover area the greatest portion of the sand prairie was 

 originally occupied by a mixed consocies, in which several species 

 of bunch-grass were well represented (PI. II; PI. Ill, Fig. i). The 

 same consocies was also of considerable importance in the Havana 

 area, and was described in a former paper (Hart and Glea- 

 son, igoy: 158-160). It was also well represented in the Ocjuawka 

 area, especially in the prairies between Keithsburg and Oquawka. 

 In the Dixon area no estimate can be made at present concerning its 

 former extent. It seems probable that over the sand prairies as a 

 whole at least two thirds of the surface was occupied by this mixed 

 growth. Although now greatly reduced in area because of cultiva- 

 tion, the remnants left show that it grew alike on the higher eleva- 

 tions and on the depressions between the hills ; that there was little 

 difference in the veg-etation as the habitat changed ; and that the 

 specific composition of the grasses varied considerably from place to 

 place, but that the g'eneral appearance of the consocies was remark- 

 ablv uniform. 



