II 





ISOETACEAE (QUILL WORT FAMILY) 61 



usually scattered among the gynosporangia, the spores 25-30 /x (average 28 /x) 

 long, minutely tuberculate. Borders of ponds and streams, s. N. H. to N. J. 

 Our largest species. 



9. I. Gravdsii A. A. Eaton. Polygamous; leaves 20-150, 12-30 cm. 

 long, 2-3 mm. in diameter, erect, reddish or dark green ; sporangia with an 

 abundance of light brown cells, |-i covered by the velum ; gynospores 351- 

 405 it in diameter, the upper hemisphere depressed, covered with short truncate 

 single columns ; androspores 22-30 it (average 26 it) long, high-cristate or tuber- 

 culate. Mass, to Ct. 



10. I. D6dgei A. A. Eaton. Leaves 10-75, the submersed 20-45 cm. long, 

 1.5-2 mm. wide, erect or spiral; emersed 10-15 cm. long, interlaced; stornata 

 many ; bast-bundles usually present ; sporangia sprinkled 



with light cells, 1-| covered by the velum ; gynospores 

 500-675 /x (average 560 /x) in diameter, sparsely beset with 

 irregular often anastomosing walls ; androspores 22-44 it 

 (average 32 /x) long, wrinkled. (/. riparia, var. canadensis 

 Engelm.; /. canadensis A. A. Eaton.) Firm soil, borders 

 of ponds and streams, Me. to B. C., southw. to Pa. FIG. 29. 



Var. Robbinsii A. A. Eaton. Leaves 15-30, 10-38 cm. long, 1-1.5 mm. wide, 

 dark green, rigidly erect, fine-pointed ; sporangia |-^ indusiate, covered with 

 brown cells ; gynospores 460-600 it (average 500 it) in diameter, thickly beset 

 with anastomosing jagged walls ; androspores 28.7-32.8 /x long, rough or slightly 

 papillose. (7. canadensis, var. JRobbinsii A. A. Eaton.) Borders of ponds 

 and streams, s. Mass, to N. Y. 



11. I. Engelmanni A. Br. Leaves 10-40, 1-4 dm. long, 1-2 mm. in diame- 

 ter, light green ; sporangia unspotted, \ or less indusiate ; gynospores 350-570 /x 



(average 450 /x) in diameter, honeycomb-reticulated with 

 thin walls ; androspores 24-29 it long, smooth. Ponds, 

 streams, and ditches, mostly in clay, N. H. and Vt. to Pa. 

 and Mo; mostly near the coast. FIG. 30. Var. GRACILIS 

 30 I Entrelmanm Engelm." is an attenuate form in shade or deep water. 

 Gynospore x 15 Var - valida Engelm. Plants larger ; leaves 50-100, 3-6 dm. 



tall, 2-3 mm. wide, often with 6 bast-bundles ; sporangia 

 |-f indusiate ; gynospores 320-570 it (average 480 it) in diameter ; androspores 

 24-30 /x (average 28 fj.) long, blunt-spinulose. N. J. to Va. 



Var. fontana A. A. Eaton. Trunk 1-2 cm. in diameter; leaves 30-50, 

 15-20 cm. long, 2 mm. wide, erect, with many stomata and six large and sev- 

 eral small bast-bundles ; velum narrow ; sporangia sparingly spotted with light- 

 brown cells ; gynospores 400-750 /x (average 500 it) in diameter, covered with 

 coarser more or less broken alveolations ; androspores as in the type. Pa. and 

 Va. ; local. 



12. I. melan6poda J. Gay. Polygamous; leaves 15-60, 1.5-3.5 mm. broad, 

 12-45 cm. tall, chestnut or black at base, with numerous peripheral bast- 

 bundles ; sporangia less than indusiate, thickly spotted ; 



gynospores 250-400 it (average 330 it) in diameter, nearly 



smooth or with low often confluent tubercles ; androspores 



23-30 /.x (average 25 it) long, spinulose. Inundated fields and 



shallow ponds, 111. and la. to Okl. and Cal. FIG. 31. Variety 31. I. melanopoda. 



PALLIDA Engelm. of the Southwest, occasionally found mixed Gynospore x 15. 



with the type in our range, differs only in having pale leaf-bases. 



13. I. Butleri Engelm. Dioecious; leaves 8-60, 7.5-22 cm. long, 0.5 mm. 

 diameter, rigid, triangular-setaceous, with wide dissepiments, narrow air- 

 canals, and four stout bast-bundles ; sheaths granular on the 

 backs ; velum none or very narrow ; sporangia mostly spotted ; 

 gynospores 400-630 it (average 570 it) in diameter, roughened 



32 I B ti with ver y sma11 warts or fragmentary crests ; androspores 28-34 it 

 Gynospore x!5 lon ' coarsely tubercled. Moist hillsides and shallow depres- 

 sions, 111. and Kan. to Tenn. and ( )kl. FIG. 32. Var. IMMACIJL\TA 

 Engelm. is a form without spots on the sporangia, growing with the typical 

 form of the species. 



