NAIADACE^, (PONDWEED FAMILY.) 431 



!• IjEMNA, L. Duckweed. Dock's-meat. 



Flowers appearing from a cleft in the edge of the frond, three together burfit- 

 ing through a thin and membranous um-shaped spathe ; two of them consisting 

 of single stamens (one developed rather earlier than the other), with thread-like 

 filaments and 2-celled anthers ; the other a 1-eelled ovary forming a utricle in 

 fruit: stigma funnel-form : ovules anatropous or half-anati-opous. — Root with 

 a sheath-like appendage on its extremity. Fronds laterally proliferous by a 

 son of budding, and producing litfle bulbets which sink to the bottom of the 

 water in autumn but rise to develop on the surface in spring, (An old Greek 

 name, of uncertain meaning.) 



§ 1. LBMNA, Schleiden. — Boot single : filaments filiform : ovtde solitari/, 



1. li. trisilica, L. Fronds oblong-lanceolate fiom a stalked base, thin, den- 

 ticulate at the tip (^'-|' long), proliferous from the side, so as to form crosses; 

 "ovule half anatropous." — Ponds; not rare: but the flowei-s little known. (En.) 



2. Ii. minor, L. Fronds roundish-obovate, thickish (aboat 2" long), 

 often grouped ; " oviUe half-anatropous ; seed lioriixmial." — Very common, man- 

 tling stagnant waters : not yet found in flower in this country. (Eu.) 



3. L<. perpusilla, Torr. Fronds obovate,thin (1"-!^" long), single or 

 grouped ; ovule anatropous ; seed erect, stiiate. — Staten Island, New York ( Tor- 

 rey), and doubtless common elsewhere. August. 



§2. SPIRODELA, Schleiden. — Boots severalin a cluster from each frond : fila- 

 meids of the stamens narrowed below : ovules 2. 



4. Ii. jpolyrrbiza, L. Fronds roundish-obovate (3" -4" long), thick, 

 rather convex beneath. — Ponds and pools. Not here found in flower. (Eu.) 



^3. TELMAT6PHACE, Schleiden. — iJoofe single: filaments of the stamens 

 enlarged in the middle : ovules and seeds 2-7, anatropous : albumen little. 



5. I>. gibba, L. Fronds obovate, nearly fiat above, tumid and spongy under- 

 neath (hemispherical), proliferous on short and very fragile stalks, therefore 

 seldom found connected (3"-4"long). — Ponds; rather rare. Not here seen 

 in flower. (Eu.) 



Ordeu 115. IVAIADACE^. (Pondweed Family.) 



Immersed aquatic plants, with jointed stems and sheathing stipules within 

 the petioles, or unth sheathing hoses to the leaves, inconspicuous mona- dioe- 

 cious or perfect flowers, which are naked or with a free merely scale-like calyx ; 

 the ovaries solitary or 2-i and distinct, 1-celled, 1-ovuled. Seed without al- 

 bumen, filled by the large embryo, often curved or hooked. Flowers usu- 

 ally bursting from a spathe, sometimes on a spadix. 



Synopsis. 



* Flowers monoecious or dioecious, axillary, naked, monandrous. 

 1. NAEAS. Pistils solitary and nalted : stigmas 2-4. 

 2 ZANNIOIIELLIA. Pistils about 4 from a cup-shaped involucre or slieath. 



