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. (Macouri). 



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, i 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. (I. Braunii Durieu.) Nova 

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

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

 son), Greenland (VaJtl). 



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 Cham plain, north end of Isle La Motte (Prin- 



gle\ 



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 delicate, 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 (Bootf). 



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 



