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. Georgiana 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 (Canby). 



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

 9' 12' long, the bast bundles often quite small or only two 

 present. New England ; Passaic River, New Jersey (Ennis). 



Var. valida Engelm. Leaves 50200, keeled on the upper 

 side, 1 8' 25' long; sporangia often linear-oblong 4" 9" long, 

 to f covered by the broad velum ; macrospores 0.32 0.48 mm. 

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

 Mark and Smithville, Pennsylvania (Porter}; Wilmington, 

 Oelaware (Canby). 



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

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

 long, unspotted, \ to \ 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). 



n. 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 0.4 mm. thick, 

 slightly tuberculate, the tubercles somewhat confluent. Hood 

 River, Oregon (Howell). 



ft Velum 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. rigida Engelm. is smaller, with 

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

 monia, near Tallahassee, Florida (Rugel); also near Manatee, 

 Florida (Garber). The variety at Lake Flirt, Florida (Gar her). 



