ISOETACEyE. 143 



green, 2' — 6' long ; sporangia orbicular — broadly-elliptic, with a 

 narrow velum ; ligula triangular, short or somewhat elongate ; 

 macrospores 0.50 — 0.80 mm. in diameter, marked all over with 

 distinct or somewhat confluent crests ; microspores smooth, 

 0.035 — 0.046 mm. long. Var. paupercula Engelm. has fewer, 

 thinner and shorter leaves and smaller spores, the microspores 

 somewhat granulate, 0.026 — 0.036 mm. long. (/. macrospora 

 Durieu.) Catskill Mountains, New York (Schweinitz), Echo 

 Lake, New Hampshire {Tuckerman), Fresh Pond, near Cam- 

 bridge, Massachusetts {W. Boott), Uxbridge, Massachusetts 

 {Robbins), Brattleborough, Vermont {Frost), Lake Superior 

 {Porter). The variety from Grand Lake, Middle Park, Colo- 

 rado {Engelmann) and Castle Lake near Mt. Shasta, California 

 {Pr ingle). 



2. I. pygmsea Engelm. Leaves 5 — 10, stout, rigid, bright- 

 green, V — i' long, abruptly tapering to a fine point, with very 

 short often almost square epidermal cells; sporangia orbicular 

 with a narrow velum ; macrospores 0.36 — 0.50 mm. thick, 

 marked with minute, rather regular, distinct or rarely confluent 

 warts; microspores brown, almost smooth, 0.024 — 0.029 mm. 

 long. Mono Pass, California {Bolander). 



3. I. Tuckermani A. Br. Leaves 10—30, very slender, 

 tapering, olive-green, 2' — 3' long, the outer recurved ; sporangia 

 mostly oblong, white or rarely brown- spotted, the upper third 

 covered by the velum; macrospores 0.44 — 0.56 mm. thick, the 

 upper segments marked with prominent, somewhat parallel and 

 branching ridges, the lower half reticulate ; microspores smooth 

 or nearly so, 0.026 — 0.032 mm. long. Mystic River, Mystic, 

 Spy, and Horn Ponds, near Boston, Massachusetts. 



* * Stomata present. 



4. I. Macounii A. A. Eaton. Leaves 5 — 12, i' — 2' long, 

 stout, acuminate, with occasional stomata near the apices, 

 reddish green ; basal wings wide ; ligula triangular-lanceolate ; 

 sporangia orbicular, i" — i^" in diameter, one-fourth to three- 

 fourths covered by the velum, thickly pale-spotted ; macro- 

 spores 0.3 — 0,57 mm., sparsely covered with very stout, short, 

 blunt, or confluent spinules, which become small papillae near 

 the equator and on the upper half appear on the commissures ; 

 microspores elliptical, 0.035 by 0.027 mm., or sometimes slightly 



