POND WEED FAMILY. 

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



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

 1803. 



' "lost. &Schmidt,Fl.Sed.384. 1824. 



81 



i8o.) 



Stem slender, forking. Leaves linear, pel- 

 lucid, acuminate or abruptly acute, #'-1' 

 ang, }^ rr -\ ff wide, numerous and crowded 

 i the upper parts of the branches, with 25-30 

 linute teeth on each edge; sheaths obliquely 

 >unded with 5-10 teeth on each margin ; 

 lit ellipsoid with very thin pericarp, i // -2 // 

 long, W-Yz" in diameter ; style long, per- 

 sistent ; stigmas short; seed smooth, shin- 

 jg, straw-colored, sculptured, though some- 

 imes quite faintly, with 30-40 rows of nearly 

 juare or hexagonal reticulations which are 

 :arcely seen through the dark pericarp. 



In ponds and streams throughout nearly all 

 Jorth America. Also in Europe. Summer. 



Naias flexilis robusta Morong, Coult. Bot. Gaz. 10 : 255. 1885. 



Stem stout, few-leaved, 3-6 long ; intrrnode* 



long. Massachusetts t<> Mit/hi^m .unl 'IYxa. 



3. Naias Guadalupensis iSpreng.) 

 Morong. Guadaloujx.- Naia>. 

 (Fig. is 



Canlinia Guadalupensis Spn UK Syrt. I: xx 



1825. 

 Naias Guadalupensis Morontr Mini T>rr Club. 



3 : Part 2, 60. 1893. 



Stem nearly capillary, i-2 long, widely 

 branched from the base. Leaves numerous, 

 6 // -9 // long, %"-%" wide, acute, opposite or 

 in fascicles of 2-5, frequently recurved, with 

 sheaths and teeth like those of N. flevilis bat 

 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, not shining. 



In ponds and lakes, Nebraska to Oregon and 

 Texas, east to Florida. Also in tropical America. 

 July-Sept. 



4. Naias gracillima (A. Br.) Morong, Thread-like Xaias. (Fig. 182.) 



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



A. Gray, Man. Ed. 5, 681. 1867. 

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



Part 2, 61. 1893. 



Dioecious, stem capillary, 6 / -i5 / long, much 

 branched, the branches alternate. Leaves nu- 

 merous, opposite or often fascicled in 3's-s's or 

 more, setaceous, j /- 2/ l n g> usually with about 

 20 minute teeth on each margin ; sheaths auri- 

 cled, with 6 or 7 teeth on each auricle, the teeth 

 standing upon setaceous divisions of the sheath ; 

 stigmas very short ; fruit oblong-cylindric, Yt" 

 l n g> *A" in diameter, slightly curved inwardly 

 or straight, the pericarp straw-colored or pur- 

 plish, marked by about 25 rows of irregularly 

 oblong reticulations ; seed not shining. 



In pools and ponds, eastern Massachusetts to 

 Delaware, Pennsylvania and Missouri. July-Sept. 



