484 NAIADACE^E. (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 flowering ; the spadix itself 

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

 short and pointed plumule from the upper end, by the side of the short cotyle- 

 don. Marine herbs, growing under water, with long and thread-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 H. B. 

 Ruppius, a German botanical author of the early part of the 18th century.) 



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

 fruiting peduncles capillary ('-!' long). Shallow bays, along the whole coast : 

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

 narrowly leaved variety with strongly pointed fruit, approaching R. rostellata, 

 Koch. June -Sept. (Eu.) 



5. POTAMOGETON, Tourn. PONDWEED. 



Flowers perfect. Sepals 4, rounded, valvate in the bud. Stamens 4, oppo- 

 site the sepals : anthers nearly sessile, 2-celled. 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) crus- 

 taceous. Embryo hooked, annular, or cochleate, the radicular end pointing 

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

 mostly rooting stems, and 2-ranked 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 Trora/zoy, a river, and 

 yft'rtoi/, a neighbor, from their place of growth.) 



The following account of the genus is contributed by DR. J. W. BOBBINS, 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. 



1. DIVERSIFOLII. Leaves of two sorts; the floating ones coriaceous, and different 



in form from the more delicate submersed ones. 



* Submersed leaves mostly with no distinction of blade and petiole, being in fact blade- 

 less more or less flattened petioles, or phyllodia, sessile, grass-like, narrowly linear, 

 or so attempted as to become flliform or capillary. 



H- Stems rather stout : stipules free from the leaves : spikes all emersed, cylindrical and 

 densely fruited : fruits fleshy and turgid, obliquely obovate : embryo coiled into less 

 or scarcely more than one turn. 



1. P. natans, L. Stem simple or sparingly branched; floating leaves all 

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

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

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



