August, 1955 



EvERS: HiLi. Pr.airies of Illinois 



387 



Table 9.— Available space per plant In the central milacre of Sampson and of I'heUley 

 hill prairies. 



three bunch-grass species are not so dif- 

 ferent in size from the plants of most 

 other herb species (most of them dicotyle- 

 dons) as to call for separate estimations 

 of a\ailable space for grasses and for other 

 herbs. 



Available space per plant for Sampson 

 and Pheglev hill prairies is given in 

 table q. 



Numbers of Plant Species for Var- 

 ious Plot Sizes. — From the species lists 

 compiled for plot sizes ranging from 1/64 

 milacre to 75 milacres, it was possible to 

 find the average number of plant species 

 in plots of several sizes and also the in- 

 crease in number of species with an in- 

 crease in area. 



Sampson Prairie. — In the central mil- 

 acre of the Sampson prairie, for plots of 

 1 64-milacre size the average number of 

 species was 3.79, the average number of 

 individuals, 30.45. One of the plots of 

 this size contained but, one species, Andru- 

 piiqon scoparius; the plot with the great- 

 est number of species contained seven, 

 Atidropcjgoti scoparius, Solidago nemoralis, 

 Houstonin nif/ricniis, Desinodium cilinre, 

 Bouleloua curtipcndula, Aijaj'e I'iryinica, 

 and Lecidea sp. 



Plots of 1/16-milacre size in the cen- 

 tral milacre contained 3 to 10 species each 

 and averaged 6.56 per plot; the number 

 of plants averaged 121.81. Quadrats of 

 1 4-milacre size in this milacre contained 

 7 to 1 1 species each and averaged 1.5 per 

 plot ; the average number of plants was 

 487.25. 



In the 9-milacre square, the species list 

 compiled by 1 /4-milacre units showed a 

 range of 5 to 1 1 species and an average of 

 7.33 per unit; plots of the 1-milacre size 

 had 9' to 13 species each and averaged 

 11.22. In the 9-iTiilacre square, a total of 

 18 species was found. Species not found 

 in the central milacre but found in one 



or more of the 8 milacres surrounding it 

 were Senecio plattensis, Carya sp. (seed- 

 ling), Aster patens, Sisyrinchium alhidiini, 

 and an unidentified moss. 



The 9-milacre plot formed a part of 

 the staked 25-milacre square. Species lists 

 were made for the 25-milacre quadrat by 

 5-milacre strips. Three species, Juniperus 

 I'irffiiiiana, Kuhnia eupatorioides, and 

 Helianthus divaricatus, not found in the 

 9-milacre plot, were found in other parts 

 of the 25-milacre quadrat, and brought 

 the total to 21 species for the 25-milacre 

 quadrat. 



The 50-milacre rectangle, fig. 10, 

 downslope from the 25-milacre quadrat, 

 was checked by 10-milacre strips. Twenty 

 species were found in this 50-milacre area. 

 Three species, Aster oblongifolius, Ely- 

 mus i/in/idensis, and Eupatorium altissi- 

 iniini. found here were not found in the 

 25-milacre unit. However, the species of 

 Carya, Opuntia, Sisyrinchium, and Hel- 

 ianthus found within the 25-milacre square 

 were absent from the larger area. In the 

 75-milacre area, 24 species were present. 



Phegley Prairie. — In the central mil- 

 acre of the Phegley prairie, for plots of 

 1 /64-milacre size the average number of 

 species was 3.94, the average number of 

 plants, 20.95. In one of the plots of tiiis 

 size only one species, A ndropogon sco- 

 parius, with two individuals, was found ; 

 the plot with the greatest number of spe- 

 cies contained eight, A. scoparius, Soli- 

 dago nemoralis, Houstonia nigricans. Ger- 

 ardia sp. (possibly C. gattingeri) , Lespe- 

 deza stipulacea. Bouteloua curtipcndula, 

 Euphorbia corollata, and L. capitata. 



Plots of 1 16-milacre size in the cen- 

 tral milacre contained 4 to 1 1 species each 

 and averaged 7.13 per plot. The number 

 of plants in plots of this size a\eraged 

 83.81. Quadrats of 1 4-milacre size in 

 this milacre contained 11 or 12 species 



