REVISION OF THE GENUS NAJAS. 405 



'Najas flexilis is a temperate species which, judging from the increasing num-ier of 

 localities for its fossil fruits in Northern Europe, was formerly more widely spread than 

 at present over the cooler parts of the north temperate zone. It is represented in the 

 warmer parts of America by K microdon, which spreads from the southern Fnited States 

 through Central America and the West Indies into South America, and as far south as 

 Uruguay. The two species are very similar in vegetative characters, but can be certainly 

 distinguished by the fruit, that of J^^ flexilis presenting a polished appearance to the 

 naked eye, while that of N. microdon shows an evident sculpturing. N. flexilis has 

 generally a stiffer habit and often a bushy growth, with generally narrower recurving 

 leaves. 



Morong (in Mem. Torr. Bot. Club, iii. no. 2, 59) states that A^ flexilis is dioecious, but 

 this is not so. The male flowers seem to be produced in fewer numbers than the female. 



8. Najas podostemox, Magn. Beitr. p. vii, t. 3. fig. 15, t. 5. figs. 16, 17 (1870), & in 

 'Ber. Deutsch. Bot. Ges. xii. (1894) 20 ; K. Schum. in Mart. Fl. Bras. iii. pt. 3, 730, 

 t. 123, fig. 3 (1894). 

 Planta effusa caulibus elongatis gracillimis flexibilibus rhombeo-dichotome ramosis ; 

 internodiis inferne elongatis denudatis superne al)breviatis habitum confertum 

 preebentibus ; foliis anguste linearibus attenuato-acuminatis flexibilibus interdum 

 recurvatis, membranaceis, manifeste serratis, dentibus cum cellulis pluribus 

 marginem superantibus, subrepandis ; vagina declivi ten era dentibus 2-3 vel inter- 

 dum 4 plus minus productis instructa ; squamulis intravaginalibus lineari-subulatis ; 

 flore masculino manifeste et longiuscule pedicellato, spatha superne in collum 

 angustum ore spiniferum producta ; perianthio apice bilabiato ad antheram unilocu- 

 larem arete apj)licito; flare femineo nudo lageniformi, stylo in stigmata 2-3 tantum 

 diviso ; friictu subfusiformi, semine parvo graciliter tessellato, cum seriebus arearum 

 subelongataruni numerosis exsculpto. 

 Shoots very long, 30 to 40 cm., or longer, scarcely 1 mm. wide in the lower part. 

 Leaves generally 7 to 10 (rarely to 14) ram. long, '7 to 1 mm. broad including the 

 marginal teeth, teeth reaching -3 mm., the lowest larger and more remote, generally 

 about 10 each side, sometimes fewer, rarely as many as 20. Sheath 1 to 1'5 mm. long, 

 by 1 mm. or slightly broader at the middle. Intravaginal scales scarcely "5 mm. long. 

 Male floiver I'D to 17 mm. long including the pedicel (o mm.), neck about '3 mm., 

 with 3 to 5 brown spine-teeth at the mouth. ]Magnus states that the flower-stalk 

 proper may become elongated within the spathe before dehiscence, pushing the flower 

 out above the spathe. Seed 11 to 1*2 (or according to Schumann nearly 1*5) mm. long, 

 about '5 mm. at its greatest diameter; testa with 25 to 30 rows of rather shallow, 

 somewhat elongated areas. 



Brazil — Prov. Alto Amazonas, Rio Maranhao (Pohl ; Vanthier), 

 I am indebted for many of the details in the above description to the descriptions and 

 figures of Magnus [1. c.) and K. Schumann (/. «?.). 



9. Najas microdon, A. Br. (PI. XL. figs. 78-91.) 



iV. microdon, A. Br. iu Sitznngsb. Ges. Naturf. Fr. Berlin, 1868, 17 ; Moroiig in Bot. Gaz. x. (1885) 256. 

 A'ar. guadahipensis, A. Br. /. c. 



3q2 



