146 OUR NATIVE FERNS AND THEIR ALLIES. 



9'— 20' or more long, with abundant stomata ; sporangia ob- 

 long—linear-oblong, unspotted, with a narrow velum ; ligula 

 elongate from a triangular base; macrospores 040—0.52 mm. 

 thick, delicately honeycomb-reticulated; microspores usually 

 smooth, 0.024—0.028 mm. long. Var. Georgimia Engelm. has 

 fewer leaves and larger (0.48—0.56 mm. thick) macrospores. 

 New England and New York, Missouri and Illinois ; the vari- 

 ety in Horseleg Creek, Floyd County, Georgia (Catiby). 



Var. gracilis Engelm. Leaves 8—12, often submerged, 

 9'— 12' long, the bast bundles often quite sm;ill or only two 

 present. New England ; Passaic River, New Jersey {Etinis). 



Var. valida Engelm. Leaves 50— 200, keeled on the upper 

 side, 18'— 25' long; sporangia often linear-oblong 4"— 9" long, 

 i to I covered by the broad velum ; macrospores 0.32—0.48 mm. 

 thick; microspores spinulose, 0.024 — 0.027 mrn. long. Warrior's 

 Mark and Smithville, Pennsylvania (Porter); Wilmington, 

 Delaware {Canhy). 



10. I. Howellii Engelm. Leaves 10—25, bright green, 

 5' — 8' long, with thick dissepiments; sporangia oval, i^" — 2^" 

 long, unspotted, i to i covered by the velum ; ligula awl-shaped, 

 as long as the sporangium ; macrospores 0.43 — 0.48 mm. thick, 

 rough with prominent, rounded, single or sometimes confluent 

 tubercles. Dalles of the Columbia, Oregon {Howell). 



11. I. nuda Engelm. Leaves 10 — 15. bright-green, 6' — 9' 

 long; sporangia oval, light-brown, attached to the base of the 

 leaves by the median line only, the velum entirely wanting; 

 ligula somewhat triangular; macrospores 0.366— 0.4mm. thick, 

 slightly tuberculate, the tubercles somewhat confluent. Hood 

 River, Oregon (Howell). 



tt Velufu complete. 



12. I. flaccida Shuttleworth. Leaves 10 — 35, light-green, 

 15' — 2° long, submerged, floating on the surface or wholly 

 emerged ; sporangia oval, 2"— 3" long, entirely covered by the 

 velum; macrospores 0.30— 0.42 mm. thick, covered with many 

 or rarely few, large flattish tubercles, distinct or confluent into 

 labyrinthiform wrinkles. Var. r/'gida Engelm. is smaller, with 

 more slender, erect, dark-green leaves, 5' — 6' long. Lake Im- 

 monia. near Tallahassee, Florida {Rugel)\ also near Manatee, 

 Florida {Carder). Tlie variety at Lake Flirt, Florida {Carter). 



