28 FLORA. 



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

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



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

 or wholly emersed in dry seasons; Leaves i<> 301 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 /1 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 // long, smooth. Lab. 

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



Isoetes echinospora robiista 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 Bouttii 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 ^ 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- 



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



confluent, almost crest-like spinules ; microspores 28-32 /u., 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 // in di- 

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

 grains of sugar ; microspores papillose, 24-28/* 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, 

 'hearing numerous stomata ; peripheral bast-bundles wanting ; ligule rather sh<>rt, 

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

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

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

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

 ders of the lower Delaware R. to Me. 



6. Isoetes foveolata A. A. Eaton. (I. F. f. 106c.) 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 < ne- 

 fourth <>r one-third of the sporange ; ligule round-ovate ; sporanges thickly sprinkled 

 with dark cells which are often collected in groups ; macrospores 3S0-560// 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 sj 

 microspores dark brown, 2: 35 // lone, densely reticulate ami usually slightly 



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

 N. II. 



7. Isoetes iiatoni Dodge. (I. 1 . f. 106b.) Amphibious from a large trunk 

 2.5-10 cm. in diameter. Leaves of the submerged plant 20-200, varying in 

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

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

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



