THE PRAIBIE-PLAIN8 CLIMAX. 



221 



"Thus it appears from the data collected during the preliminary investiga- 

 tion of the structure and development of the vegetation of the sand-hills of 

 Nebraska that we have here two prominent successional series. One of these 

 originates under the pecuhar xerophilous enviromnent of a sand-dune complex, 

 while the other begins in an extremely hydrophilous situation. And further- 

 more, as a tentative conclusion, it appears that each of these series progresses 

 toward, and will ultimately culminate in, the relatively mesophytic sod-form- 

 ing associations of the prairie-grass formation." 



Lake Michigan 



Chlamydomonas Assoc. 



Juncus alpinus insignis 



Assoc. 



t 



Triglochin palustris 



Assoc. 



I Lemna-Riccia Assoc. 



Carex oederi pumfla- 



Cyperus rivularis Assoc 



i 

 Sabatia-Linum Assoc. 



Juncus 



River 

 Planl<to/i Assoc. 



Chara Assoc, 

 ♦ 

 Potamogeton Assoc. 



Castalia-Nymphaea Assoc. 



w 



RAnuncUlus aquatiFis 

 capillaceus Assoc. 



Menyanthes-S'agittaria /^ssoc. 

 Cfirex Assoc. 



balticus 



littoralis Assoc. 

 Potenti la anserina Assoc. 



Liatris scariosa Assoc. 



\ 



Juncus torreyl 

 Assoc. 



Potentilla fruticosa 

 Assoc. 



Populus-Salix-Cornus 

 Tliicket Assoc. 



\ 



Caramagrostis cam 

 I Assoc. 



Iris Assoc. 



\ 



Phragmites-Typlia Assoc, 

 icir, 

 Sclrpus ann 



Cladiuri Assoc 



Scirpus validus Assoc, 

 sricanus Assoo. 



Prairie Assoc. 



Quercus vetutina Assoc 



I 

 Quercus-Carya Assoc. 



f 

 Ulmus-Acer Assoc. 



♦ 

 Acer saccharum Assoc. 



Fig. 9. — Diagram of development of maple-beech climax, showing course of hydrosere. 



After Gates. 



SUBSERE. 

 Clements (1897 : 968) drew attention to the succession in the abandoned 

 fields and roadways of western Nebraska, and pointed out that the latter were 

 colonized by Helianthus petiolaris, Salsola tragus, and Malvastrum cocdneum. 

 They are characterized for a long time by Gutierrezia and Artemisia frigida, 

 and, even when these are driven out by Stipa comala, the latter also shows the 

 vigorous growth typical of the undershrubs and grasses of such areas. 



