144 OUR NATIVE FERNS AND THEIR ALLIES. 



larger, finely and densely papillose, or rarely blunt tuberculate. 

 Pools on an extinct volcano, Atka Island, lat. 52° N., long. 175° 

 W. {Macoun). 



5. I. echinospora Durieu, var. Braunii (Dur.) Engelm. 

 Leaves 13 — 15, erect or spreading, tapering, green or reddish- 

 green, 3' — 6' long, generally with few stomata toward the tip 

 only; sporangia orbicular — broadly-elliptic, spotted, ^ to f 

 covered by the broad velum ; macrospores 0.40 — 0.50 mm. thick, 

 covered with broad, retuse spinules, sometimes somewhat con- 

 fluent and then dentate and incised at the tip; microspores 

 0.026—0.030 mm. long, smooth. (/. Braunii Durieu.) Nova 

 Scotia, New England, New York, New Jersey, Pennsylvania, 

 Ontario, Michigan {Gillman), Head of Bear River, Utah ( Wat- 

 son), Greenland {Vahl). 



Var. robusta Engelm. Stouter; leaves 25 — 70,5' — 8' long, 

 with abundant stomata all over their surface ; velum covering 

 one half of the large, spotted sporangia; macrospores 0.36 — 0.55 

 mm. thick. Lake Champlain, north end of Isle La Motte (Prin- 



Var. Boottii (A. Br.) Engelm. Leaves 12 — 20, erect, bright - 

 green, 4' — 5' long, with few stomata mostly near the tip; spo- 

 rangia nearly orbicular, pale-spotted, f or more covered by the 

 broad velum ; macrospores 0.39 — 0.50 mm. thick, with longer, 

 more slender and d»licate, generally simple spinules; micro- 

 spores 0.026 — 0.030 mm. long. (/. Boottii A. Br.) Round 

 Pond, Woburn, and in brook in Tofit Swamp, Lexington, 

 Massachusetts {Booti). 



Var. muricata (Dur.) Engelm. Leaves 15 — 20, flaccid, 

 green, 6' — 12' long, with very few stomata; sporangia broadly 

 oval, pale-spotted, about half covered by the velum ; macro- 

 spores 0.40 — 0.58 mm. thick, with shorter and more confluent, 

 sometimes almost crest-like spinules; microspores 0.028 — 0.032 

 mm. long, slightly rough on the edges. (/. muricata Durieu.) 

 Woburn Creek and Abajona river near Boston, Massachusetts 

 {Boott). 



6. I. Bolanderi Engelm. Leaves 5 — 25, erect, soft, bright- 

 green, tapering to a fine point, 2'— 4^' long, with thin walls and 

 generally few stomata ; sporangia broadly oblong, mostly un- 

 spotted, with a narrow velum ; ligula triangular ; macrospores 



