484 NAIADACE^. (PONDWEED FAMILY.) 



envelopes, consisting of 2 sessile stamens, each with 2 large and separate an- 

 ther-cells and 4 small sessile ovaries, with a single campylotropous suspended 

 ovule : stigma sessile, depressed. Fruit of little obliquely-ovate pointed drupes, 

 each raised on a slender stalk which appears after tlowcring; the spadix itself 

 also then raised on an elongated thread-form peduncle. Embryo ovoid, with a 

 short and pointed plumule from the ui)pcr end, by the side of the short cotyle- 

 don. — Marine herbs, growing under water, with long and thiead-like forking 

 stems, and slender almost capillary alternate leaves, sheathing at the base. 

 Flowers rising to the surface at the time of expansion. (Dedicated to //. D. 

 liu/i/iins, a German botanical author of the early part of the 1 8th century,) 



1. R. maritima, L. Leaves linear-capillary ; nut ovate, obliquely erect; 

 fruiting peduncles capillary (|^' - 1 ' long). — Shallow bays, along the whole coast : 

 also Onondaga Lake (near salt springs). New York, J. A. Pdine. Chiefly a 

 narrowly leaved variety with strongly pointed fruit, approaching K. rostcllata, 

 Koch. June -Sept. (Eu.) 



5. POTAMOGETON, Tourn. Fondweed. 



Flowci's perfect. Sepals 4, rounded, valvate in the bud. Stamens 4, oppo- 

 site the sepals : anthers nearly sessile, 2-cellcd. Ovaries 4 (rarely only one), 

 with an ascending campylotropous ovule : stigma sessile or on a short style. 

 Fruit drupe-like when fresh, more or less compressed : endocarp {nutlet) crns- 

 taeeous. Embryo hooked, annular, or cochleatc, the radicular end pointing 

 downwards. — Herbs of fresh, or one in brackish, ponds and streams, with jointed 

 mostly rooting stems, and 2-rankcd leaves, which are usually alternate or im- 

 perfectly opposite ; the submersed ones. pellucid, the floating ones often dilated, 

 and of a firmer texture. Stipules membranous, more or less united and sheath- 

 ing. Spikes sheathed by the stipules in the bud, mostly raised on a peduncle to 

 the surface of the water. (An ancient name, composed of 7rora/Aoj, a river, and 

 yeiTcov, (I ml(ihbor, from their place of growth.) 



The following account of the genus is contributed by Dr. J. W. Robbins, of 

 Uxbridge, Mass. — By fruit, the full-grown fresh or macerated fruit is intended ; 

 by nutlet, that with the fleshy outer portion or epicarp removed. All except 

 No. 15 flower in summer: the month mentioned indicates the season of the 

 maturation of the fruit, which, especially, should be collected. 

 § I. DiVERSiFOLii. Leaves of tico sorts ; the flocitinrj ones coriaceous, and different 



in form from the more delicate submersed ones. 

 * Submersed leaves mostli/ loilh no distinction of blade and petiole, being in fact blade- 



hss more or less flattened /letioies, or phi/llodia, sessile, grass-like, narrowljj linear, 



or so attenuated as to become flii form or capillar j/. 

 •*- Stems rather stout : stipules free from the leaves : .spikes all cmersed, cijlindriral and 



denselji fruitfd : fruits fle^hij and turnid, oUUqnclj ohovate : enihri/o coiled into less 



or saircelfi more than one turn. 



1. P. nutans, L. Stem simi>le or fparinglg branched ; floating leaves all 



long-petioled, elliptical or ovate, somewhat cordate at base, obtuse but with a 



blunt point, 21 -29ncrved ; upper submersed leaves lanceolate, early perishing, 



the lower (later in the season) very slender (3' -7' long, barely a line wide); 



