212 Cyperaceae Carex 



525. CAREX [Dill.] L. Sedge* 



A genus of nearly 2000 species and the largest genus of vascular plants 

 in Indiana. Few species have any economic value but the ecological role 

 of the genus is of great importance. The species of marshes and muddy 

 borders of lakes which form extensive colonies, and to some extent the 

 less gregarious species, comprise an essential step in the successional stages 

 from open water to the culmination in climax forest or prairie. Much of 

 the fertile soils of our region today would still be barren mudflats were it 

 not for the part played by these sedges in the conversion of the once vast 

 boggy areas into a turf, thus enabling less hydrophytic plants to become 

 established and add further to the fertility of the soil. 



For the identification of species in this genus it is nearly always neces- 

 sary to have a specimen with ripe fruit (perigynia) and as a rule the 

 roots are also essential. In the key closely related species have been grouped 

 for convenience into sections, roughly corresponding in size to most of the 

 genera in other groups. After only a slight acquaintance with the sedges 

 of an area it is generally possible to recognize at sight the group or section 

 to which an unknown species belongs, especially since a few of the sections 

 (Ovales, Bracteosae, Laxiflorae, Acutae, and Lupulinae) will include the 

 great majority of the individuals found in the field. 



The most recent and exhaustive treatment of the species of Carex in our 

 area is K. K. Mackenzie's monograph in North American Flora 18 : 1-478. 

 1931-35. In the following account this monograph has been freely used in 

 the preparation of the keys and in giving distribution. 



NATURAL KEY TO THE SECTIONS OF INDIANA CARICES 



Stigmas two; achenes lenticular; spikes usually bisexual, the lateral sessile 



Subgenus Vignea. 



Stigmas three; achenes triangular; or if stigmas two and achenes lenticular, the 



lateral spikes peduncled; spikes normally unisexual Subgenus Eu-Carex. 



Subgenus Vignea 



Terminal or all spikes androgynous; perigynia not subterete. 



Culms arising singly or few together from long-creeping rootstocks. 



Heads elongate, 2-7 cm long; culms not branching; perigynia thin- or wing- 

 margined; not plants of sphagnum bogs. 

 Perigynia thin- but not wing-margined, ovate-orbicular, thick-plano-convex, 

 3.4-5 mm long; spikes all androgynous; plants of wet habitats 



1. § INTERMEDIAE, p. 218. 



Perigynia narrowly wing-margined, oblong-lanceolate, plano-convex, 4.75-6 mm 

 long; lowest spikes usually pistillate, the middle staminate, and terminal 



androgynous; plants of dry sandy habitats 2. § Arenariae, p. 218. 



Heads ovoid, 0.5-1.2 cm long; culms becoming decumbent and branching; perigynia 

 neither thin- nor wing-margined, oblong-obovate, thick-plano-convex, 2.5-3.75 



mm long; plants of sphagnum bogs 3. § Chordorrhizae, p. 219. 



Culms cespitose, the rootstocks sometimes short-prolonged with short internodes but 

 not long-creeping. 

 Perigynia abruptly contracted into the beak; culms not flaccid and not flattening 

 in drying. 

 Spikes few (generally 10 or fewer), usually greenish. .4. § Bracteosae, p. 219. 



* Contributed by Frederick J. Hermann, University of Michigan. 





