28 FLORA. 



verging ridges ; microspores 35-46 // long, smooth. In water 0.3-1.6 m. deep, 

 Lab. to the N. W. Terr., south to K. Mass, and N. J. Also in Europe and Asia. 



2. Isoetes Tuckermani A. Br. (I. F. f. 103.) Submerged or rarely partly 

 or wholly emersed in dry seasons ; leaves 10-30, very slender, tapering, olive- 

 green, quadrangular, 5-8 cm. long, without peripheral bast-bundles, the outer 

 recurved ; sporange oblong, mostly white, its upper one-third covered by the velum; 

 macrospores 440-560 // in diameter, with wavy somewhat parallel and branching 

 ridges on the upper half, separated by the three converging ridges, the lower 

 covered with an irregular network ; microspores 26-32 // long, nearly smooth. In 

 ponds, Newf. to Middlesex County, Mass., clustered in shallow water. 



3. Isoetes echinospora Braunii (Durieu) Engelm. (I. F. f. 104.) Submerged 

 or rarely emersed ; leaves 12-25, tapering, soft, reddish -green, 7-20 cm. long, with- 

 out peripheral bast-bundles, bearing stomata only toward the tip ; sporange orbicu- 

 lar or broadly elliptic, spotted, one-half to three-fourths covered with the velum ; 

 macrospores 400-500 // in diameter, covered with broad spinules which are often 

 slightly confluent and incised at the tips ; microspores 26-39 /' l n g> smooth. Lab. 

 and Greenland to Alaska, south to N. J., Penn. and Utah. 



Isoetes echinospora robusta Engelm. Much larger than the preceding, leaves 25-70 

 or even more 12-30 cm. long, with abundant stomata throughout. With the preceding. 



Isoetes echinospora Boottii Engelm. Leaves 12-20, soft, erect, bright green, 

 10-13 cm. long, with a few stomata near their tips ; sporange nearly orbicular, with pale 

 spots, two-thirds or more covered by the velum ; macrospores 390-500 M in diameter, with 

 longer and more slender simple spinules ; microspores 26-30 M. long. In ponds, Middlesex 

 County, Mass., usually submerged. 



Isoetes echinospora muricita (Durieu) Engelm. Leaves 15-20, flaccid, bright green, 

 15-30 cm. long, bearing few stomata ; sporange broadly oval, with pale-spots, about one- 

 half covered by the velum ; macrospores 400-580 p. in diameter, with shorter and more 

 confluent, almost crest -like spinules ; microspores 28-32 /ot, slightly rough on the edges. 

 Submerged in running water in tributaries of Mystic Pond, Middlesex County, Mass. 



4. Isoetes saccharata Engelm. (I. F. f. 105.) Amphibious or uliginous with 

 a flat depressed trunk. Leaves 10-20, olive- green, pale at the base, spreading. 5-8 

 cm. long, quadrangular ; stomata numerous ; sporange oblong, unspotted, with a 

 narrow velum covering only one-fourth or one-third of its surface ; peripheral bast- 

 bundles wanting ; ligule triangular, rather short ; macrospores 400-470 /4 in di- 

 ameter, with very minute distinct or rarely confluent warts as if sprinkled with 

 grains of sugar ; microspores papillose, 24-28 /.i long. In mud overflowed by the 

 tides, Wicomico and Nanticoke rivers, E. Md. and near Washington, D. C. 



5. Isoetes riparia Engelm. (I. F. f. 106.) Amphibious or uliginous, usually 

 emersed ; leaves 15-30, deep green, rather rigid, 10-20 cm. long, quadrangular, 

 bearing numerous stomata ; peripheral bast-bundles wanting ; ligule rather short, 

 triangular ; sporange mostly oblong, distinctly spotted with groups of brown cells, 

 one-fourth or rarely one-half covered with the velum ; macrospores 450-650/4 in 

 diameter, marked with distinct or anastomosing jagged crests or somewhat reticu- 

 late on the lower side ; microspores 28-32 ju long, more or less turberculate. Bor- 

 ders of the lower Delaware R. to Me. 



6. Isoetes foveolata A. A. Eaton. (I. F. f. io6c.) Amphibious from a 

 bilobed or rarely trilobed base ; leaves 15-70, stout 5-15 cm. long, pinkish even 

 when dry or rarely dark green ; stomata scattered found only near the tips ; no 

 peripheral bast-bundles ; monoicous or becoming dioicous ; velum covering one- 

 fourth or one-third of the sporange ; ligule round-ovate ; sporanges thickly sprinkk-d 

 with dark cells which are often collected in groups ; macrospores 380-560/4 in di- 

 ameter, covered beneath with very thick-walled reticulations, the openings appear- 

 ing like little pits ; reticulations elongate on the upper surface of the spore ; 

 microspores dark brown, 22-35 // long, densely reticulate and usually slightly 

 papillose. In muddy banks of the Pautuckaway River, Epping and E. Kingston, 



7. Isoetes liatoni Dodge. (I. F. f. io6b.) Amphibious from a large trunk 

 2.510 cm. in diameter. Leaves of the submerged plant 20200, varying in 

 length up to 7 dm., marked with an elevated ridge on the ventral side ; leaves of 

 the emersed plant shorter, 7.5-15 cm. long, stomata abundant ; peripheral bast- 

 bundles irregular in occurrence or often wanting ; velum covering one-fourth of the 



