NAIADACEAE. 



VOL. I. 



2. Naias flexilis (Willd.) Rost. & 

 Schmidt. Slender Naias. Fig. 213. 



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



1803. 



A", 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, Y'-i" 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 (Spreng.) 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"-i" 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 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, i" 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 



