Pound and Clements : method of detekmining species. 23 



ing to do with the mode of disposition of individuals. But given 

 a copious, gregario-copious or sparse species, there still remains 

 something more to be said before the abundance of the species 

 is fairly indicated. Collation of the results of a large number 

 of enumerations has shown that six grades of copious plants 

 may be recognized readily. The first, in which the average 

 number of individuals in a plot five meters square exceeds 200, 

 corresponds to copious.' As examples, there may be cited from 

 the prarie formations Amor-pha cancscens, with an average of 

 309 in the prairie region, Aster vmltifiorus with an average of 

 275 in the prairie region and about 230 in the sand hill region ; 

 from the herbaceous layer of woody formations, Verbesina 

 altcrni folia (which is almost gregarious at times), with an aver- 

 age of 245. To the second degree (copious') those species may 

 be assigned in which the average number of individuals in a 

 plot is from 150 to 200, such as Plantago Parshii (162) in the 

 Peppergrass-Cactus formation in the transition area between 

 the sand hill region and the foot hill region. Those species 

 with an average ranging from 100 to 150 may be assigned to 

 the third degree (copious^). Examples are : Aster sagittifoh'tcs, 

 which has an average of 133 in the herbaceous layer of the Bur- 

 oak-Elm- Walnut formation in the Mississippi basin region and 

 Solidago rupestris, which has an average of 104 in the Sporo- 

 bolus-Koelcria-Panicitm formation in the prairie region. In 

 the fourth degree (copious^) those species may be included 

 which have an average of from 50 to 100, such as Glycorhiza 

 lepidota in the river valleys in the sand hill region, where its 

 average is 83. All of the foregoing are of sufficient abundance 

 to be included in the general term " copious," taking the latter 

 to represent a quantitative idea as well as the manner of associ- 

 ation of the individuals. Where the average falls below 50 and 

 exceeds 5, we call the species " subcopious." Comparison and 

 collation of statistics has shown that subcopious species fall into 

 two groups, in one, which we call subcopious,^ the average 

 does not fall below 15. Examples are : Kuhnistera Candida in 

 the Sporoholtis-Koeleria-Panicum formation in the prairie re- 

 gion, where it has an average of 18, Solidago mollis in the 

 Peppergrass-Cactus formation in the transition area between 

 the sand hill and foot hill regions, where its average is slightly 

 over 20, and Artejuisia gnaphalodcs in the transition between 

 the prairie and the sand hill regions, where its average is 16. 



