ZANNICHELLIACEAE. 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: Potamogeton 

 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 2-1 1 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. 



I 1. Ruppia maritima 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 hrackish water throughout the archipelago : Coast of 

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

 of the OUi World. Ditch-grass. 



