Crests crowded ; sporangia densely spotted 

 Gynospores reticulated. 

 Plants of medium size; androspores smooth 

 Plants large ; androspores spinulose . 



ISOETACEAE (QUILLWOKT FAMILY) 59 



0. Leaves reddish or olive-green. 



Gynospores averaging 440 /u. in diameter, with small pits . . 4. I.foveolata. 

 Gynospores averaging 510 /u. in diameter, with thin irregular 



walls (4)7. foveolata, v. plenospora. 



c. Leaves green d. 

 d. Gynospores with jagged crests. 



Gynospores averaging 600 /u. in diameter; crests tall, mostly 



simple 5. 7. riparia. 



Gynospores averaging less than 550 jn in diameter ; crests low, 



simple or reticulated. 



Leaves 1-2.5 mm. in diameter ; trunks 2-lobed . . .6. 7. saccharata. 

 Leaves 1-1.5 mm. in diameter; trunks 2-5-lobed (6) 7. saccharata, v. Amesii. 



d. Gynospores with slender or lagged spines. 



Leaves short, stout, spreading 1. I. echinospora. v. Braunii. 



Leaves long, fine, spiral (7) 7. echinospora, v. muricata. 



3. Plants of the extreme edges of ponds or streams, emersed most of the 

 summer, with stomata and bast-bundles. PALWTRES A. A. 

 Eaton e. 

 e. Bast-bundles 4, one at each front angle and one at each end of the 



dorsi-ventral partition /. 



f. Polygamous ; androsporangia rare ; gynospores appearing abortive. 

 Bast-bundles often absent; gynospores with labyrinthiform 



ridges 8. 7. Eatoni. 



Bast-bundles always present; gynospores with truncate col- 

 umns 9. 7. Gravesii. 



/. Monoecious. 



Gynospores with coarse irregular crests. 

 Crests loose ; sporangia slightly spotted . ... 10. 7. Dodgei. 



ded ; sporangia densely spotted . (10) 7. Dodgei, \. Robbinsii. 



. 11. 7. Engelmanni. 

 . (11) 7. Engelmanni, v. valida. 

 e. Bast-bundles 4, with accessary ones in the periphery 



Monoecious; gynospores crested, somewhat reticulated (11) 7. Engelmanni, v.fontana. 

 Polygamous ; gynospores small, smooth or with low tubercles or 



wrinkles 12. 7. melanopoda. 



4. Plants of dry situations ; leaves setaceous ; bast-bundles 4 ; stomata 



many ; velum none. TERRESTRES A. Br 18. 7. JSutleri. 



1. I. macr6spora Dur. Leaves 10-30, 2 mm. in diameter, erect, round, dark 

 green, rather blunt; velum covering | of the unspotted sporangium ; gynospores 

 600-800 it in diameter, the upper faces traversed by thin parallel 



walls, the lower hemisphere reticulated ; androspores 36-47 fj. 

 (average 42 /x) long, smooth. GaspS Co., Que., and Me. to 

 Ont. and Minn. FIG. 25. 



Var. heter6spora A. A. Eaton. Leaver 50-150, 2 mm. in 

 diameter, 5-8 cm. long, rigid, erect, tapering to a sharp point; 

 sporangia spotted $-f indusiate ; gynospores 540-675 /x (some 

 abnormally 1100-1134 /x) in diameter, densely covered with 

 thick jagged convoluted crests, often reticulated below ; andro- -J L macros P. 

 spores 30-40 /x (average 35 /x) long, dark brown, papillose. ^y nos P r ' 

 (/. heterospora A. A. Eaton.) Jordan Pond, Mt. Desert, Me. 



2. I. Tuckermani A. Br. Trunk often 3-lobed, small ; leaves 10-40, 1 mm. 

 or less in diameter, 4-15 cm. long, reddish or olive green, sometimes with a 

 few stomata but no bast-bundles ; sporangia small, rarely spotted, or more 

 covered by the velum; gynospores 450-750 /x (average 600 M) in diameter, 

 parallel-walled or reticulated above, more or less reticulated below ; andro- ' 

 spores 25-38 /x (average 30 /x) long, slightly rough. Sandy ponds, Me. to Ct. 



Var. borealis A. A. Eaton. Trunk bilobed ; leaves 10-100, 3-25 cm. long, 

 1-1.5 mm. thick, green or reddish, straight or recurved; stomata none; 

 gynospores 600-785 /x in diameter, more coarsely reticulated ; androspores 42 /x 

 long, finely spinulose. N. Y. to N. H. and Lab. 



Var. HarvSyi (A. A. Eaton) Clute. Trunk 2-lobed, 1.6-3 cm. in diameter; 

 leaves 50-140, purple-bronze, 2.5-3 mm. in diameter, 5-6 cm. long, strongly re- 

 curved ; stomata none ; sporangia unspotted, -^ covered by the velum ; gyno- 

 spores 526-648 n (average 560 /x) in diameter : androspores 30-39.6 /x (average 

 34 it) long. (7. Harveyi A. A. Eaton. )TN. Y. and Mass, to Nfd. 



3. I. hieroglyphica A. A. Eaton. Leaves 10-20, 6-7.5 cm. long, 1-2 mm. in 

 diameter, blunt, recurved ; sporangia not spotted, covered by the velum ,- 



