Characters of the family. Slender, branching, submerged aquatics. Flowers sessile or pedicelled. Sterile flowers with a double perianth, the exterior one entire or 4-horned at the apex, the interior one hyaline, adhering to the anther; stamen sessile or stalked, 1-4-celled, apiculate or 2-lobed at the summit. Fertile flowers of a single ovary which tapers into a short style; stigmas 2-4, subulate. Mature carpel sessile, ellipsoid, its pericarp crustaceous. Seed conformed to the pericarp, the raphe distinctly marked. [Greek, water-nymph.]

About 10 species in fresh water all over the world. There is one other American species known only from Florida and Cuba. Type species: Naias marina L.

Sheaths broadly rounded, their margins entire or with a few large teeth.

1.

N. marina.

Sheaths narrowly and obliquely rounded, each margin with 5-10 minute teeth; leaves linear.

Seeds shining, with 30-50 rows of faint reticulations.

2.

N. flexlis.

Seeds dull, with 16-20 rows of strongly marked reticulations.

3.

N. guadalupensis.

Sheaths auriculate; leaves filiform.

4.

N. gracillima.

1 Naias L Sp Pi 1015 1753 212

1. Naias Marina L. Large Naias

Fig. 212

Naias marina L. Sp. PI. 1015. 1753.

Naias major All. Fl. Ped. 2: 221. 1785.

N. marina gracilis Morong, Coult. Bot. Gaz. 10: 255. 1885.

Naias marina recurvata Dudley, Cayuga Fl. 104. 1886.

Naias gracilis Small, Fl. S. E. U. S. 40. 1903.

Dioecious, stem stout, compressed, commonly armed with teeth twice as long as their breadth. Leaves opposite or verticillate, 6"-12" long, about 1" wide, with spine-pointed teeth on each margin and frequently several along the back; sheaths with rounded lateral edges; fruit large, 2"-2 1/2" long, the pericarp as well as the seed rugosely reticulated, tipped with a long persistent style and 3 thread-like stigmas; seed not shining.

In lakes. Central New York to Florida, west to California- Summer. Also in Europe.

1 Naias Marina L Large Naias 213

2. Naias Flexilis (Willd.) Rost. & Schmidt. Slender Naias

Fig. 213

Caulinia flexilis Willd. Abh. Akad. Berlin, 95.

1803. N. flexilis Rost. & Schmidt, Fl. Sed. 384. 1824. Naias flexilis robusta Morong, Coult. Bot. Gaz.

10: 255. 1885.

Stem slender or stout, 3°-6° long, forking. Leaves linear, pellucid, acuminate or abruptly acute, 1/2'-l' long, 1/2"-1" wide, numerous and crowded on the upper parts of the branches, with 25-30 minute teeth on each edge; sheaths obliquely rounded with 5-10 teeth on each margin; fruit ellipsoid with very thin pericarp, 1"-2" long, i"-i" in diameter; style long, persistent; stigmas short; seed smooth, shining, straw-colored, sculptured, though sometimes quite faintly, with 30-40 rows of square or hexagonal reticulations scarcely seen through the dark pericarp. In ponds and streams throughout nearly all North America. Also in Europe. Summer.

3. Naias Guadalupensis (Spreng.) Morong. Guadaloupe Naias

Fig. 214

Caulinia guadalupensis Spreng. Syst. 1: 20. 1825. Naias guadalupensis Morong, Mem. Torr. Club, 3: Part 2, 60. 1893.

Stem nearly capillary, 1°-2° long, widely branched from the base. Leaves numerous, 6"-9" long, \"1/4"-1/2" wide, acute, opposite or in fascicles of 2-5, frequently recurved, with sheaths and teeth like those of N. flexilis but generally with 40-50 teeth on each margin of the leaf; fruit about 1" long; pericarp dark and strongly marked by 16-20 rows of hexagonal or rectangular reticulations which are transversely oblong; seed straw-colored.

In ponds and lakes, Pennsylvania to Oregon, Florida and Texas. Tropical America. July-Sept.

3 Naias Guadalupensis Spreng Morong Guadaloupe Nai 2143 Naias Guadalupensis Spreng Morong Guadaloupe Nai 215

4. Naias Gracillima (A. Br.) Magnus. Thread-Like Naias

Fig. 215

Naias Indica var. gracillima A. Br.; Engelm. in A.

Gray, Man. Ed. 5, 681. 1867. Naias gracillima Magnus, Beitr. 23. 1870.

Monoecious, stem capillary, 6'-15' long, much branched, the branches alternate. Leaves numerous, opposite or often fascicled in 3's-5's or more, setaceous, -2' long, usually with about 20 minute teeth on each margin; sheaths auricled, with 6 or 7 teeth on each auricle, the teeth standing upon setaceous divisions of the sheath; stigmas very short; fruit oblong-cylindric, i" long, \" in diameter, slightly curved inwardly or straight, the pericarp straw-colored or purplish, marked by about 25 rows of irregularly oblong reticulations. In pools and ponds, eastern Massachusetts to Delaware, Pennsylvania and Missouri. July-Sept.