ISOETACEAE 31 



1. ISOETES L. 



The only genus. Owing to their aquatic habitat and apparently local distribu- 

 tion, these plants are popularly little known. Some species are called Quillwort. 



Velum incomplete or wanting. 



Amphibious: megaspores honeycombed-reticulated. 1. /. Engelmannii. 



Terrestrial: megaspores tuberculate. 



Polygamous: leaves 15-60, often blackish at the base. 2. I. melanopoda. 



Dioecious: leaves 8-15, bright green. 3. /. Butleri. 



Velum complete. 



Megaspores dark-colored: leaves 5-6 cm. long. 4. I. melanospora. 



Megaspores light-colored: leaves 40-60 cm. long. 5. /. Jlaccida. 



1. Isoetes Engelmdnnil A. Br. Amphibious, usually partly immersed when 

 mature. Leaves 25-100, light green, quadrangular, tapering, 22-50 cm. long, bearing 

 abundant stomata: peripheral bast-bundles present: sporanges oblong or linear- 

 oblong, unspotted: velum narrow: megaspores 400-520^1 in diameter, covered with 

 honeycomb-like reticulations: microspores 24-28 ^ long, mostly smooth. 



In ponds and ditches, rooting in mud, Maine to Delaware, Pennsylvania and Missouri. 

 — Represented in our range by /. Engelmannii Oeorgidna Engelm., which has fewer leaves 

 and slightly larger megaspores, and is known from Georgia ; and by I. Engelmannii Garo- 

 linidna A. A. Eaton, which has stouter leaves, a broader velum and larger brown densely 

 muricate microspores ; it occurs in the mountains and middle country of North Carolina. 



2. Isoetes melandpoda J. Gay. Terrestrial, with a subglobose deeply 2-lobed 

 trunk. Leaves 15-60, slender, erect, bright green, with a blackish shining base, 12-15 

 cm. long, 3-angled, bearing stomata throughout and well developed peripheral bast- 

 bundles; ligule 3-angled, awl-shaped: sporanges mostly oblong, spotted, with a nar- 

 row velum: polygamous: megaspores 250-400 /x in diameter with low more or less 

 confluent tubercles, often united into worm-like wrinkles, or almost smooth: micro- 

 spores 23-28 fj, long, spinulose. 



On moist prairies and in overflowed fields, Iowa to Illinois, Missouri and Texas. — The 

 Texan form has larger leaves with pale bases. 



3. Isoetes Butleri Engelm. Terrestrial, with a subglobose trunk. Leaves 8-15, 

 bright green, paler at base, triangular, 4.5-18 cm. long, bearing numerous stomata, 

 and with well developed peripheral bast-bundles, thick dissepiments and small air 

 cavities: sporanges usually oblong, spotted: velum very narrow or none: ligule small, 

 triangidar: dioecious: megaspores 500-630 /i in diameter, with distinct or confluent 

 tubercles. 



On rocky hillsides, Missouri and Indian Territory. — A variety, I. Butleri immaculdta 

 Engelm., growing in the barrens about Nashville, Tennessee, has longer leaves, unspotted 

 sporanges and spinulose microspores. 



4. Isoetes melandspora Engelm. Trunk flat, slightly 2-lobed. Leaves 5-10, 

 distichous, slender, 5-6 cm. long, light green : sporanges orbicular or nearly obcordate, 

 1-2 mm. long, covered by the velum: ligule triangular, obtuse: megaspores 350^50^1 

 in diameter, with distinct or confluent warts, dark-colored: microspores 28-31 fi long. 



In shallow excavations in granite, slopes and summit of Stone Mountain and Little 

 Stone Mountain, middle Georgia. 



5. Isoetes fldccida Shuttlw. Leaves 10-85, light green, 4-6 dm. long, submersed 

 or emersed: sporanges oval, 4-6 mm. long: megaspores 300^20 fi in diameter, 

 covered with numerous, or rarely few large flattish tubercles, these distinct or con- 

 fluent into labyrinthiform wrinkles. 



In lakes and ponds, western and peninsular Florida. — A variety, I. flaccida rlgida 

 Engelm., from Lake Flirt, is smaller, and has more slender and erect leaves. 



SuBKiNGDOM SPERMATOPHYTA. Seed-bearing Plants. 



Plants producing seeds and flowers. A seed contains an embryo con- 

 sisting of a short stem (radicle, caulicle or hypocotyl), one, two or several 

 rudimentary leaves (cotyledons) and a terminal bud (plumule). 



Ovules and seeds borne on the face of a bract or a scale: stigmas wanting. Class 1. Gymnospermae* 

 Ovules and seeds in a closed cavity (ovary) : stigmas present. Class 2. Angiospermae. 



Class 1. GYMNOSPERMAE. 



Carpel represented by a scale or disk upon whose face are borne the 

 ovules and on which the naked seeds are matured. 



