NAlADACEiE. (POND-WEED FAMILY.) 823 



or cordate at base. Peduncles as thick as stems; spike dense, cylindri- 

 cal, .03 to .05 long; sex)als round-rTiorriboid ; sides of the turgid nutlet 

 ^oith a deep depression in the middle — June — Stagnant -water. 



* * All the leaves aWce, suhnerged and alternate {except those under the 

 peduncles lohich arc nearly opposite), ovate or lanceolate. Stipiulesfree. 



2. P. liiccii§, L. If Stem branched. Leaves merrdjranous, pellu- 

 cid, short-p)etiol€d, cuneatc at base, ovate to ovate-obloDg and lanceo- 

 late, .00 to .1 long, .01 to .03 broad, serrate-roughened at margin. 

 Peduncles thicker than steins, thickened above. Spike dense, cylindri- 

 cal, .03 to .03 long; sepals transversely elliptical; nutlets obliquely 

 elliptical, somewhat flattened, when recent with obtuse, slightly kcelc<l 

 margin — Summer — Lake of Yamiini. 



3. P. pcrfoliatus, L. % Stem branched. Leaves many-nerved, 

 membranous, pellucid, cordate-clasjnng at base, ovate to ovate-lanceo- 

 late, .03 to .OG long, with roughish margins. Peduncles as thick as 

 stems, longer than the short-cylindrical spike ; se\)ix\s short-ovate ; recent 

 nutlets obovate, compressed, with obtuse margin — Summer — Jordan. 



4. P. cri§pii§, L. 21 Stem forked, somewhat flattened. Leaves 

 membranous, sessile, oblong to oblong-linear, .05 to .08 long, .005 to 

 .01 broad, serrulate, crisp-wavy at margin. Peduncle as thick as stem, 

 three to four times as long as somewhat interrupted spike ; sepals ovate ; 

 nutlets ovate, compressed, ending in a slender, recurved beak nearly as 

 long as they — Summer — Arabia Petrcca ; Haurtin ; Damascus. 



Var. Plilalensis, Post. (Bull. Herb. Boiss., L 409.) Leaves 

 scarcely or not at all serrulate; spikes globular to oblong, 7-30-flowered 

 — Lake Phiala {Birliet-er-Rdm). 



■■ * * All the leaves suhnerged, grass-like, alike, and {icith the exception of 

 those svMending the pedimcles, which are nearly opjjosite) alternate. 



Stipules free. 



5. P. Piiiala3 , Post. (Bull. Herb. Boiss., L 409.) li Stem Ali- 

 form, much branched; leaves membranous, pellucid, sessile, capillary, 

 3-nerved, short-mucronate, .03 to .03 long, .001 broad. Peduncles 

 longer than leaves; spike short, 2-4-flowercd, interrupted; nutlets 

 scarcely compressed, oblique, rhomboid-orbicular, coarsely tuherclcd at 

 lack, mucronate at the hase and apex of the inner margin — June — Lake 

 Phiala {Birket-cr-Ildm). 



* * * * All the leaves suhnerged, grass-like, alternate, the hase produced 



into a sheath adaate to the stipule. 



6. P. pcctiiiaUis, L. % Stem filiform, much branched. Leaves 

 setaceous, obsoletely grooved, acute, 1-nerved, transversely veined. 

 Peduncles elongated ; flowers in remote, somewhat one-sided clusters, 

 forming long, slender, interrupted spikes ; sepals somewhat broader than 



long; nutlets semilunar, somewhat compressed, with obtuse back, and 

 the inner margin straight, ending in a short beak — Summer — Birket- 

 Buswayeh (Lebanon). 



■■^ * =*= * * All the leaves suhnerged, and opposite, the lower without stijntles, 

 the floral one or two with a stijndc on one or loth sides. 



7. P. deusus, L. 2^ Stems cylindrical, forked. Leaves decus- 

 sate, sessile, clasjnng, memh-anous, pellucid, elliptical to ovate-lanceolate, 



