832 NAIAD ACEiE. (POND- WEED FAMILY.) 



leaves, ending in a long, slender, stiff raceme; i^edicels stiff, shorter 

 than fruits ; fruit appressed to axis, linear, tapering at base, angled ; 

 carpels 3, somewhat terete, subulate, tapering-aristate at base, separat- 

 ing at first by lower part from axis -- Summer — Marshes of the Zerqa 

 (ifaifa). 

 Order CXIX. IVAIADACEiE, Endl. (Pond-Weed Family). 

 Immersed af[uaiic plants with jointed stems and sheath- 

 ing stipules loithin the petioles y or with sheathincjhases to the 

 leaves^ inconspicuous flowers^ which are nahed, or ivith a 

 free, scale-lihe calyx ; the ovaries solitary^ or 2-4, distinct, 1- 

 celled, 1-ovided — Flowers perfect or monoecious or dioecioiis. 

 Stamens 1-4, with sliort lilaments or 0, anthers 2-4-celled. 

 Carpels 1-8, free, sessile, or at length pedicelled, 1-ovuled ; 

 ovuie erect, pendulous, or laterally attached. Fruit consist- 

 ing of membranous carpels or nutlets, or drupe-like. Albu- 

 men 0. Embryo hooked or straight — Plants, some of them 

 growing in fresh, others in salt water. 



* Flowers spiked, perfect or polygamous. 

 t Perigonium of A divisions. Floating in fresh or brackish water. 



1. rOTAMOGETON. Flowers perfect. Sepals, stamens and ovaries 4. 



f t Perigonium 0, Salt water plants. 



2. KUPPIA. Uerbs with filiform leaves and perfect flowers. Anther cells and ovaries 4. 



3. POSIDOXIA. Herbs with strap-shaped leaves. Stamens 3, ovary 1. 



* * Floioers axillary, perfect, moncecious, dimcious, or polygamous. ■ 

 t Perigonium 0. 



4. ZANXICHELLIA, Flowers monoecious, umbelled. Fresh water plants. 



5. ZOSTERA. Flowers perfect, spiked, with a kind of spadix and spathe. Marine plants. 

 C. CYMODOCEA. Flowers dioecious, solitary, clustered, cymose ; anthers equal. Marine 



plants. 

 7 HALODULE. Distinguished from the last by the inequality of the anthers. Marine 



plants, 

 ■f t Perigonium hyaline. 

 8. NAIAS, Mononcious or dioecious, submerged, fresh-water plants, with linear leaves. 



1. POTAMOOETON, L. Pond- Weed. 



Flowers perfect, spiked. Perigonium herbaceous, its 4 divisions 

 short-clawed, valvate in aestivation. Anthers 4, subsessile, attached in 

 front of divisions, 2-celled, the cells some%vhat separated. Carpels 4, 

 erect, 1-ovuled, style short or 0, stigma peltate. Ovule attached to 

 ventral suture below its tip, campy lotropous. Nutlets 4, or by abortion 

 1-2, somewhat drupaceous, sessile, 1-secded; endocarp hard, albumen 

 0. Embryo hooked — Plants growing in fresh or brackish water. 



* Lower leaves submerged^ alteimate, the floral floating, nearly opposite., 

 dissimilar. Stipules free. 



1. P. iiatans, L. % Stem long, nearly simple. Leaves all long- 

 petiulod, the submerged ones oblong to lanceolate, reduced before 

 tlowering to petioles by the decay of the lamina, the floating ones 

 Icathcri/, ovate to ovate-oblong, .05 to .15 long, more or less rounded 



