416 



ORDEK 159. FIL1CES. 



a Fertile stemfe never branching, the sterile with simple, whorled branches.. NOB. 1,8 

 a Fertile stems at length, like the sterile, with compound, whorled branches. .Nos. 3, 4 



b Stems with whorls of simple branches from the middle joints Nos. 5, 6 



b Stems mostly simple, large, 20-40-furrowed Nos. 7 8 



b Stems always simple, very slender, 8-9-furrowed Nos. 10, 11 



1 E. arvense L. Fertile stems erect, 6 8', simple ; sterile 12-14-furrowed, with sim- 



ple, ascending, 4-angled branches ; sheath cut into long dark-brown teeth ; spike 

 612", oblong. Can. to Va. and Ky. The sterile stems appear after the fertile. 

 ft. serbtinum. Sterile plant also producing a late spike of fruit. Pa. (Porter). 



2 E. Telmateia Ehr. Ivory H. Sterile stem 2 5f, ivhite, about 30-furrowed, its 30 



branches 4-angled ; fertile stems simple ; sheaths with subulate teeth. L. Superior. 



3 E. sylvaticum L. Stems 12- or 13-furrowed, both kinds with compound, deflexed, 



angular branches, 9 16'. Woods and low grounds. North. 



4 E. prat^nse Ehr. Stems 10-12-furrowed, both kinds soon producing simple, straight 



branches, in several whorls ; branches 3-angled. N. W. 



5 E. limosum L. Pipes. Stems 2 3f, smooth, erect, 15-20-striate, mostly with a 



few irregular, simple, 5-sided branches near the middle ; sheaths white above, with 

 1520 teeth, tipped with black. Shores and swamps. 



6 E. palustre L. Sts. 1 l|f, erect, with 68 prominent striae ; branches few, sheaths 



with as many pointed teeth as striae. Marshes, N. Rare in the United States. 



7 E. Jaevlgatum Braun. Stems 2 3f, erect, simple or some branched ; sheaths long 



(6 7'0, close, green, with 2025 black teeth ; branch sheaths 8-toothed. Miss. River. 



8 E. robust urn Braun. Sts. 2 4f, very stout, some branched above ; sheaths shoit 



(34"), close, with 40 (in the branches 11) deciduous teeth, and a black band near the 

 base, rarely with another above. River banks, W. States to California ! 



9 E. li yen* ale L. Scouring Rush. Stems all simple, erect, 2f, very rough with sili 



cious points ; sheaths ashy-white, black at base and summit, short (2 3"), with about 



20 subulate, awned, deciduous teeth. Con- 

 spicuous in wet shades. 



10 E. variegatum Schleicher. Simple 

 (branched from base), slender, straight, 

 6 12'. 5-9-furrowed ; sheaths very short, 

 with brown bristle-tipped teeth. N. Rare. 



1 1 E. scorpIoldesMx. Sts. tufted, fili- 

 form, 4-8', recurved, 3-4-furrowed ; sheaths 

 black, teeth 3 or 4, scarious and bristle- 

 tipped. Woods, Penn., and N. 



OIIDEK CLIX. FILICES. FERNS. 



Stem a perennial, creeping, horizon- 

 tal rhizome, or sometimes erect and 

 tree-like. Fronds (fruit-bearing leaves) 

 variously divided, rarely entire, with 

 mostly forked veins and drdnate 

 vernation. Fruit occupying the back 

 or margin of the fronds arising from 

 the veins. Sporangia (spore-cases) of 

 one kind, scattered, or clustered in 

 son, 1 -celled, containing numerous 

 minute spores. 



Fijr. 560, Polypodiy.m vuljrare, frond pinnate. 561, 

 ,T<)2 One of the sori enlarged, showing the sporan- 

 iii and discharging its spores. 561, A sorus of 

 NVi. Side view uf the same. 



* leaflet of the frond enlarged. 

 fria. 503, One Kpormiire furthe 

 &-;ii linm ni.ir^iii.ile cmert-'i ui 



