Jones: Flora of Illinois, 5. Ophioglossaceae 33 



3. Sheaths about as long as broad, short-cylindrical, appressed, ashy-gray, 

 with a black band near the base; internodes rough-tuberculate; moist 

 sandy soil, common. \E. rohustum A. Br ; E. hyemale of Am. auth., 

 not L.; E. hyemale var. affi7ie (Engelm.) A. A. Eaton} Tall Scour- 

 in'g-rush E. prealtum Raf. 



3. Sheaths slightly longer than broad, dilated upward and somewhat fun- 

 nelform, green, and usually with a narrow black rim; internodes 



smooth; sandy soil, common. Smooth Scouring-rush 



E. laevigatum A. Br. 



2. Stems low, slender, usually 5-10-angled; teeth of the sheaths persistent. 



4. Stems 15-30 cm. tall, 2-4 mm. thick, 5-10-2rooved; central cavity 



one-third the diameter of the stem; sheaths 5-12-toothed; cones 



8-10 mm. long; moist sandy soil in the n. half of the state. [£. 



nelsoni (A. A. Eaton) Schaffnerj Variegated Scouring-rush 



E. variegatum Schleich. 



4. Stems 5-15 cm. tall, 1-2 mm. thick, 6-angIed and -grooved, tufted, 

 slender, flexuous, solid; sheaths mostly-3-toothed; cones 3-5 mm. 

 long; moist ground. Lake Co E. scirpoides Michx. 



1. Stems annual, flexible; stomata scattered; cor/as blunt. 

 5. Stems all alike, green, usually branched at maturity. 



6. Stems 10-30-angled; central cavity one-half or more the diameter of the 

 stem; sheaths tight; along ditches or in marshes. [E. limosum L.} 

 Water Horsetail E. fluviatile L. 



6. Stems 5-10-angled; central cavity about one-sixth the diameter of the 

 stem; sheaths loose; wet soil, not common. Peoria, Woodford, and 

 Tazewell counties. Marsh Horsetail E. palustre L. 



5. Stems of two kinds, the sterile green and branched, the fertile whitish or 

 brownish, appearing in early spring and soon withering; moist sandy 

 soil, common, particularly on railroad embankments. Field Horsetail.... 

 E. arvense L. 



5. Ophioglossaceae Presl — Adder's-tongue Family 



1. Sterile blade simple, entire; venation reticulate; sporangia in two rows in a simple 



slender spike 1 . Oph'wglossum 



1. Sterile blade pinnately divided; venation free; sporangia in a panicle.. ..2. Bolrvchium 



1. Ophioglossum L. — Adder's-Tongue 



1. Sterile blades usually 2-5, oval, apiculate, the principal veins 13 or more, 

 forming broad areolae containing numerous included veinlets; spores 

 pitted; hillsides, banks, thickets, chiefly on limestone, rare. Cave-in-Rock, 

 Hardin Co., E. J. Palmer 15469 0. engelmanni Prand 



1. Sterile blades usually solitary, or sometimes 2, oval, obtuse, the principal 

 veins 7-11, forming narrow areolae containing few included veinlets; 

 spores reticulate; m-eadows, open woods, swamps, moist thickets, rare. 

 Jackson and Union counties. [O. vulgatum of Am. auth., not L.; O. 

 arenarium E. G. Britt.} O. pusillum Raf. 



