ZANNICTIELLIACEAE. 5 



inserted on the claws of the perianth-segments. Anthers sessile. Ovaries 4, 

 sessile, distinct, 1-celled, 1-ovuled, attenuated into a short style, or with a 

 sessile stigma. Fruit of 4 drupelets, the pericarp usually thin and hard or 

 spongy. Seeds crustaceous, campylotropous, with an uncinate embryo thickened 

 at the radicular end. [Greek, in allusion to the aquatic habitat.] About 65 

 species, mostly natives of temperate regions. Type species: Potaviogeton 

 natans L. 



1. Potamogeton heterophyllus Schreb. Spic. Fl. Lips. 21. 1771. 



Stems slender, compressed, much branched, sometimes 4 m. long. Floating 

 leaves pointed at the apex, mostly rounded or subcordate at the base, 1.5- 

 10 cm. long, 8-30 mm. wide, 10-18-nerved, on petioles 2-10 cm. long; submerged 

 leaves pellucid, sessile, linear-lanceolate, acuminate, cuspidate, rather stiff, 2-15 

 cm. long, 2-16 mm. wide, 3-9-nerved, the uppermost often petioled; peduncles 

 often thickened upward, sometimes clustered; stipules spreading, obtuse, 1.5-2.5 

 cm. long; spikes 1.8-4 em. long; fruit roundish or obliquely obovoid, 2-3 mm. 

 long, 1-2 mm. thick, indistinctly 3-keeled; style short, obtuse, apical; apex of 

 the embryo nearly touching the base, pointing slightly inside of it. 



In fresh water pools and ditches. Great Bahama, Andros, New Providence, 

 Great Exuma : — North America and Europe. Pondweed. 



2. RUPPIA L. Sp. PI. 127. 1753. 



Slender, widely branched aquatics with capillary stems, slender alternate 

 1-nerved leaves tapering to an acuminate apex, and with membranous sheaths. 

 Flowers on a capillary spadix-like peduncle, naked, consisting of 2 sessile 

 anthers, each with 2 large separate sacs attached by their backs to the peduncle, 

 having between them several pistillate flowers in 2 sets on opposite sides of the 

 rachis, the whole cluster at first enclosed in the sheathing base of the leaf. 

 Stigmas sessile, peltate. Fruit a small obliquely-pointed drupe, several in each 

 cluster and pedicelled; embryo oval, the cotyledonary end inflexed, and both 

 that and the hypocotyl immersed. [Name in honor of Heinrich Bernhard 

 Eupp, a German botanist.] In the development of the plants the staminate 

 flowers drop off and the peduncle elongates, bearing the pistillate flowers in 2 

 clusters at the end, but after fertilization it coils up and the fruit is drawn 

 below the surface of the water. Three or four species, widely distributed, the 

 following typical. 



1. Ruppia maritlma L. Sp. PI. 127. 1753. 



Stems usually whitish, often 1 m. long, the internodes irregular, naked. 

 Leaves 2-8 cm. long, 1.5 mm. or less wide; sheaths with a short free tip; 

 peduncles in fruit sometimes 0.3 m. long; pedicels 4-6 in a cluster, 1-3.5 cm. 

 long; drupes with a dark hard shell, ovoid, about 2 mm. long, often oblique or 

 gibbous at the base, pointed with the long style, but varying much in shape ; 

 forms with very short peduncles and pedicels, and with broad, strongly marked 

 sheaths occur. 



In shallow salt and brackish water throughout the archipelago : — Coast of 

 Eastern North America ; Bermuda ; Cuba to Trinidad ; temperate and tropical regions 

 of the O'd World. Ditch-giiass. 



