ISOETACE^. 145 



0.30—0 45 mm. thick, marked with minute low tubercles, rarely 

 confluent into wrinkles ; microspores deep-brown, 0.026—0.031 

 mm. long, spinuiose, rarely smooth. (/. Californica Engelm.) 

 Western Colorado i^Bi andegee), Utah, California, to Washing- 

 ton. 

 § 2. AfHphibi'otis, partially emerged ; stomata always present. 

 * Periplieral bast-bundles absent. 

 t Velum partial. 



6. I. saccharata Engelm. Trunk usually flat, depressed ; 

 leaves 10 — 20, awl-shaped, spreading, olive-green, 2' — 3' long; 

 sporangia oblong, spotted, with a narrow velum ; ligula trian- 

 gular; macrospores 0.40 — 0.47 mm. thick, covered with very 

 minute, distinct warts, which are sometimes a little confluent ; 

 microspores papillose, 0.024 — 0028 mm. long. Banks of 

 Wicomico river, below Salisbury, and of Nanticoke river. East- 

 ern Maryland {Canby). 



7. I. riparia Engelm. Leaves 15 — 30, slender, rather rigid, 

 deep-green, 4'- — 8' long, with numerous stomata ; sporangia 

 mostly oblong, distinctly brown-spotted, i or |^ covered by the 

 velum; macrospores 0.45--0.65 mm. thick, marked with isolated 

 or anastomosing, jagged crests; microspores more or less tuber- 

 culate, 0.028 — 0.032 mm. long. Banks of Delaware River from 

 Burlington to Wilmington, Delaware ; Uxbridge, Massachusetts 

 {Robbins); Brattleborough, Vermont (i^r^.y/); MsXne (CMckerzng) ; 

 Crow River, Hastings County, Ontario {Macouii). 



tt Velum complete. 



8. I. melanospora Engelm. Trunk flat, only slightly 

 bilobed ; leaves 5 — 10, distichous, slender, tapering, light-green, 

 2' — 2\' long; sporangia orbicular or almost obcordate, i" — i' 

 long, entirely covered by the velum; ligula short triangular, 

 obtuse ; macrospores 0.35 — 0.45 mm. long, roughened with 

 distinct or rarely somewhat confluent warts, dark-colored ; 

 microspores smoothish or slightly papillose, 0.028 — 0.031 mm. 

 long. In shallow excavations in granite rock. Stone Mountain, 

 Georgia {Canby). 



** Peripheral bast-bundles present. 

 t Velu})i partial or etitirely wanting. 



9 I. Engelmanni A. Br. Leaves 25 — 100, light-green, 



XQ 



