Genus i. 



NAIAS FAMILY, 



i. Zannichellia palustris L. Horned 

 Pondweed. Fig. 211. 



Zannichellia palustris L. Sp. PI. 969. 1753. 

 Z. intermedia Torrey ; Beck Bot. 385. 1833. 



Stems capillary, sparsely branched, the rhi- 

 zome creeping, the roots fibrous. Leaves i'-3' 

 long, i" or less wide, acute, thin, i-nerved 

 with a few delicate cross-veins ; spathe-like 

 envelope separate from the leaves and fruits 

 at maturity; fruits 2-6 in a cluster, i"-2" 

 long, sometimes sessile, sometimes pedicelled, 

 sometimes the whole cluster peduncled; style 

 persistent, 4"-i" long; plant flowering and 

 ripening its fruit under water. 



In fresh or brackish water, nearly throughout 

 North America, except the extreme north. 

 Widely distributed in the Old World. July-Sept. 



Family 4. NAIADACEAE (Lindl.) 

 Asch. Linnaea 35 : 160. 1867. 



Submerged marine or fresh-water herbs with fibrous roots and slender, branch- 

 ing stems. Internodes spiny or unarmed. Leaves alternate, opposite, or whorled, 

 the blades linear, spiny on the margins or the back, or both, acute or obtuse at the 

 apex, sometimes tipped with one or more subulate spines, sheathing at the base. 

 Leaf-sheaths rounded or auriculate, entire or with spinulose teeth. The 2 intra- 

 vaginal scales minute and hyaline. Flowers monoecious or dioecious, solitary in 

 the axils. Staminate flowers with a double perianth-like envelope, the inner 

 hyaline, the outer 4-horned or entire. Stamen 1, sessile. Anthers 1-4-celled. 

 Pistillate flowers of a single pistil. Style short or wanting. Stigmas 2-4 and 

 sometimes intermingled with 1-3 stigmoids. Fruit a sessile drupelet, the solitary 

 seed filling the pericarp. The seed apparently smooth and shining, or reticulated 

 with angled or roundish areolae. Embryo straight. Only the following genus : 



1. NAIAS L. Sp. PI. 1015. 1753. 



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. i. 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. flexilis. 



Seeds dull, with 16-20 rows of strongly marked reticulations. 3. N. guadalupensis. 



Sheaths auriculate ; leaves filiform. 4. N. gracillima. 



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 oppo- 

 site or verticillate, 6"-i2" long, about 1" wide, with 

 spine-pointed teeth on each margin and frequently sev- 

 eral along the back ; sheaths with rounded lateral edges ; 

 fruit large, 2"-2i" 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 Califor- 

 nia. Summer. Also in Europe. 



