NAIADACEAE. 



VOL. I. 



In 



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, \'-\' long, \"-\" 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, 

 i "-2" long, \"-\" in diameter; style long, per- 

 sistent; 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, 

 ponds and streams throughout nearly all North America. Also in Europe. Summer. 



3. Naias guadalupensis ( Sprang. ) Morong. 

 Guadaloupe Naias. Fig. 214. 



Caulinia guadalupensis Spreng. Syst. i: 20. 1825. 

 Naias guadalupensis Morong, Mem. Torr. Club, 3 : 

 Part 2, 60. 1893. 



Stem nearly capillary, i-2 long, widely branched 

 from the base. Leaves numerous, 6"-o/' long, 

 i"-J" wide, acute, opposite or in fascicles of 2-5, 

 frequently recurved, with sheaths and teeth like 

 those of N. flcxilis but generally with 40-50 teeth 

 on each margin of the leaf; fruit about i" 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. 



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'-is' long, much 

 branched, the branches alternate. Leaves numer- 

 ous, opposite or often fascicled in 3's-s'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, ' long, i" in diam- 

 eter, slightly curved inwardly or straight, the peri- 

 carp 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. 



Family 5. ZOSTERACEAE Demort. Anal. Fam. 65, 66. 1829. 



EEL-GRASS FAMILY. 



Perennial marine plants with creeping rootstocks and flattened, branching 

 stems. Leaves all alternate, 2-ranked, linear, flat or complicate, acute or obtuse 

 at the apex and sheathing at the base. Flowers monoecious or dioecious, arranged 



