822 NAIAD ACE J5. (POND-WEED FAMILY.) 



leaves, endiug in a long, slender, stiff raceme; pedicels 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 b}^ lower part from axis — Summer — Marshes of the Zerqti 

 (Haifa). 



Order CXIX. NAIAI>ACEiE, Endl. (Pond-Weed Family). 

 Immersecl aquatic ])lanU with jointed stems and sheath- 

 ing stipides within the jpetioles^ or loith sheathing hases to the 

 leaves^ inconsjncuous flowers ^ which are naked ^ or with a 

 free^ scaledihe calyx ; the ovaries solitary ^ or 2-i, distinct, 1- 

 celled, 1-ovuled — Flowers perfect or monoecions or dioecious. 

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

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

 ovule 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. 

 ■f Perigonium of A divisions. Floating in fresh or brackish icatcr. 



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



t t Perigonium 0. Salt water plants. 



2. EUPPIA. Herbs with filiform leaves and perfect flowers. Antlier cells and ovaries 4. 



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



* * Flowers aziUary, perfect, monmcious, dicecious, or polygamous. 

 ■j- Perigonium 0. 



4. ZAN^ICHELLIA, Flowers monoecious, umbelled. Fresh water plants. 



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

 G. CYMODOCEA. Flowers dioecious, solitary, clustered, cyraose ; anthers equal. Marine 



plants, 

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



plants, 

 f t Perigonium hyaline. 

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



1. POTAMOOETOIV, 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 somewhat 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-seeded; endocarp hard, albumen 

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



* Lower leaves siibmerged, alternate, tlie floral floating, nearly opposite, 

 dissimilar. Stipules free. 



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

 jjetiolod, the submerged ones oblong to lanceolate, reduced before 

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

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



