124 



Najadaceae; Zosteraceae 



1. Najas marina L. N. major All.; N. fluviatilis Poir. 



Ibara-mo. Stems much branched, smooth or sparsely 



spinulose; leaves rigid, linear, 2-4 cm. long, 2-3 mm. wide, flat, 

 remotely spinescent-toothed; sheath broadly rounded, entire; 

 fruit ellipsoidal-oblong, 4-6 mm. long; seeds minutely apicu- 

 late. July-Sept. Ponds; Hokkaido, Honshu, Shikoku, Kyu- 

 shu. ^Widely distributed. 



2. Najas tenuicaulis Miki. Hime-ibara-mo. Stems 

 much branched, sometimes sparingly spinulose; leaves 2-2.5 

 cm. long, about 1 mm. wide, with few marginal teeth; sheath 

 semirounded, entire or with few minute teeth; stigmas 3; 



fruit 4-5 mm. long, 1.2-2 mm. wide, ellipsoidal. July-Oct. 



Honshu; rare. 



3. Najas ancistrocarpa A. Br. Musashi-mo. Stems 

 branched; leaves 15-20 mm. long, slightly recurved, about 0.5 

 mm. wide, minutely toothed on margins; sheath semirounded, 

 with few minute spines on margins; seeds prominendy curved, 

 about 2.5 mm. long, fusiform-lanceolate, longitudinally striate. 

 Honshu; rare. 



4. Najas oguraensis Miki. O-torige-mo. Relatively 

 rigid annual with smooth branched stems; leaves subulate- 

 linear, rather rigid, 3-4 cm. long, about 0.8 mm. wide, the 

 superficial cells of seeds transversely narrow-oblong. July- 

 Sept. Honshu, Shikoku. 



5. Najas minor All. N. marina L. pro parte To- 



RiGE-Mo. Plants much branched; leaves subulate-linear, 



more or less recurved, 1-2 cm. long, 0.5 mm. wide, denticulate; 

 sheaths semirounded, minutely spinescent-toothed; seeds about 

 3 mm. long, 0.8 mm. wide, lanceolate, the superficial cells 



transversely narrow-oblong. July-Oct. Honshu. Eurasia 



and Africa. 



6. Najas yezoensis Miyabe. Ito-ieara-mo. Stems 

 slender, much branched; leaves rather rigid, linear-acicular, 

 2.3-3 cm. long, about 0.3 mm. wide, denticulate; sheaths broad, 

 rounded, minutely spinescent on margin; seeds oblong, 2.5-3 

 mm. long, the superficial cells longitudinally narrow-oblong. 

 Sept. Hokkaido. 



7. Najas japonica Nakai. N. gracillima Miki, non Mag- 

 nus Ito-torige-mo. Stems slender and much branched; 



leaves narrowly linear, about 1.5 cm. long, slightly com- 

 pressed, about 0.2 mm. wide, with 7-10 teeth on each side; 

 sheath rounded, sparingly and minutely spinescent on mar- 

 gin; seeds lanceolate, about 2 mm. long, about 0.5 mm. wide, 

 the superficial cells longitudinally linear-elongate. July- 

 Oct. Honshu, Shikoku, Kyushu. 



8. Najas indica (Willd.) Cham. Caulina indica Willd. 



Sagami-torige-mo. Stems elongate, diffuse; leaves linear, 



1.5-2.5 cm. long, minutely spinulose on margin; sheaths semi- 

 rounded, with few minute spines on margin; seeds about 2.5 

 mm. long, 0.6-0.7 mm. wide, superficial cells hexagonal, as 



broad as long. July-Oct. Honshu. India, Malaysia, and 



Philippines. 



9. Najas graminea Del. 2V. serristipula Maxim.; N. 



graminea var. serristipula (Maxim.) Nakai Hossu-mo. 



Stems slender and much branched; leaves acicular, 1.5-2.5 cm. 

 long, 0.3-0.5 mm. wide, minutely and rather densely denticu- 

 late; sheaths auricula te, narrowly deltoid, with minutely 

 toothed margin; seeds broadly lanceolate, about 2.5 mm. long, 

 0.6 mm. wide, often striate, the superficial cells minute, angled. 



July-Sept. Honshu, Shikoku, Kyushu. Africa, Eurasia, 



and Australia. 



Fam. 36. ZOSTERACEAE Ama-moKa Eelgrass Family 



Dioecious or monoecious marine rhizomatous herbs; stems elongate or short, branched, often compressed; leaves distichous, 

 flat, ribbonlike, sheathed at base; flowers on a spadix subtended by a spathe, sometimes provided with a hyaline bract; staminate 

 flower consisting of a subsessile 1-locular anther; pistillate flower consisting of a 2-carpelIate, 1-locular ovary; style terminated 

 by 2 stigmas. Two genera with more than 10 species. 



lA. Plants monoecious, sometimes stoloniferous; ovary and fruit ovate; stems elongate 1. Zostera 



IB, Plants dioecious, rhizomatous, caespitose; ovary and fruit cordate; stems short 2. Phyllospadix 



1. ZOSTERA L. Ama-mo Zoku 



Submersed dioecious herbs of saline water, usually with slender stolons; stems compressed, often branched; leaves flat and 

 ribbonlike, distichous, sheathed at base; spadix surrounded by a spathe; flowers alternately arranged on one side of the spadix, 

 the staminate consisting of one sessile, 1-locular anther, the pollen filiform; pistillate flowers consisting of 1 pistil, the ovary 

 attached on back near the middle; style elongate, the stigmas 2, filiform; fruit flask-shaped, membranous, irregularly dehiscent, 

 beaked; seed soUtary, longitudinally ribbed, narrowly oblong. Cosmopolitan, with about 10 species. 



lA. Leaves 3-15 mm. vifide. 

 2A. Leaves 3-7 mm. wide. 



3 A. Plants with slender, elongate stolons; leaves 3-5 mm. vi^ide 1. Z. marina 



3B. Plants caespitose, without stolons; leaves about 7 mm. wide 2. Z. caespitosa 



2B. Leaves 10-15 mm. wide. 



4A. Leaves abruptly acute; seeds with indistinct longitudinal striations 3. Z. caulescens 



4B. Leaves refuse; seeds without striations 4. Z. asiatica 



IB. Leaves 1.5-2 mm. wide; rhizomes slender and creeping 5. Z. nana 



1. Zostera marina L. Ama-mo. Rhizomes elongate; Honshu, Shikoku, Kyushu; common. Eurasia and N. 



leaves elongate, 3-5 mm. wide, rounded at apex, 5-7 nerved, America. 



the sheaths without auricles; inflorescence without appendage 2. Zostera caespitosa Miki. Suge-ama-mo. Plant 



on margin; seeds oblong, about 4 mm. long, longitudinally caespitose, the rhizomes not elongate, estoloniferous; leaves 



striolate. June- Aug. Shallow muddy sea water; Hokkaido, about 7 mm. wide, 5-7 nerved, retuse, with minutely rough- 



