1921] Fernald & Weatherby — Equisetum fluviatile or E. limosum 45 



to grow: here, however, both may develop side by side. The plant 

 here treated as f. minus seems at first sight to have varietal charac- 

 ters. But these characters re-appear in basal branches of typical 

 E. limosum; and Eaton, in a note on one of the sheets in the herb- 

 arium of the New England Botanical Club, states that he has ob- 

 served this form to be produced where a freshet had deposited sand 

 on a bed of typical plants and that, after some years, it reverted to 

 the typical form. It seems best, therefore, to consider it as a reduced 

 ecological state of E. limosum. 



The more striking forms, which seem to deserve some recognition, 

 are given, with their synonymy, below. 

 Culms simple or merely with a few solitary or scattered, 

 commonly long and strongly ascending branches. 

 Culms stout, 3.5-7.5 mm. in diameter in dried material; 

 sheaths of mature primary culms usually closely 

 appressed, their linear-lanceolate teeth mostly over 

 2 mm. long and black for their whole length. ...... 1. E. limosum. 



Culms slender, 1.5-3 mm. in diameter in dried material; 

 sheaths usually rather loose, their teeth deltoid- 

 lanceolate, mostly less than 2 mm. long and black 



only in'the upper half 2. f. minus. 



Culms with definite whorls of 4-16 slender ascending or 

 spreading branches from the median and upper nodes. 



Branches sterile .- .- 3 - f - ^erlicillatum. 



Branches, or some of them, bearing strobiles at their 



apices 4 - f - Polystachium. 



1. Equisetum limosum L. Sp. PI. 1062 (1753). E. Heleochans 

 Ehrh. Hannov. Mag. (1783) Stueck 18, 286, ace to Roth, Beitr. u. 

 158 (1788). E. limosum 0. aphyllum Roth, Tent. Fl. Germ. m. 9 

 (1800). E. fluviatile, "Spielart" a. praecox G. F. W. Mey. Chlons 

 Hanov. 668 (1836). E. fluviatile simplex Rupr. Symb. 92 (1845). 

 E. fluviatile* limosum Hartm. Skand. Fl. ed. 5, 216 (1849). E. li- 

 mosum a. genuinum Gren. & Godr. Fl. Fr. iii. 644 (1855). E. limosum, 

 f. Linnaeanum Doell, Fl. Baden, 64 (1857). E. limosum, var. sim- 

 plex Milde, Gefaess-Crypt. Schlesiens, 448 (1858). E. limosum, var. 

 Linnaeanum Milde, Monog. Equiset. 342 (1865). E. fluviatile /3. 

 limosum Hartm. Skand. Fl. ed. 11, 548 (1879). E. Heleochans, f. 

 limosum Klinge, Arch. Naturf. Soc. Dorpat,Ser. 2, vin.410 (1882). 

 E. Heleocharis, B. limosum Aschers. & Graebn. Syn. Mitteleur. Fl. 

 i. 136 (1896).— Labrador to Alaska, so. to New York, Indiana, Illinois, 

 Wyoming and Washington. 



2. Forma minus A. Br. in Doell, Rhein. Fl. 30 (1843).* E. uhgi- 

 nosum Muhl. in Willd. Sp. PI. v. 4 (1810). E. limosum 0. minus A. 

 Br. Am. Journ. Sci. xlvi. 86 (1844). E. limosum, var. uhginosum 

 Milde, Monog. Equiset. 343 (1865). E. Heleocharis, i.uliginosum 



i The form is here published without author citation as if it were Doell 's own; 

 but in the Fl. Baden he attributes it to Braun. 



