490 THE IfAIAB FAMILY. 



in breadth, with 3, 5, or even 7 more or less distinct parallel nerves. Flow- 

 ering sheath near the base of the floral leaves, from 1 to li or near 2 inches 

 long. Tlie flattened peduncle narrow-linear, and said to be always without 

 the horizontal appendages of the dwarf Z. Seeds oblong, marked by longi- 

 tudinal furrows. 



Common near the sandy or muddy edges of the sea, in most parts of the 

 world, usually at or below low-water mark, and often thrown up in great 

 quantities by the tide. Abundant round the British Isles. Fl. summer, or, 

 according to some, in spring only. 



2. Dwarf Zostera. Zostera nana, Both. 

 (Eng. Bot. Suppl. t. 2931.) 



Closely resembles the smaller forms of the common Z., of which it is be- 

 lieved by some to be a mere variety. The leaves are usually from a few 

 inches to near a foot long, very narrow, with only 1 or rarely 3 distinct 

 nerves ; the flowering sheath about half an inch long, and the flattened pe- 

 duncle inside has to every ovary a little transverse appendage or band. 

 Seeds shorter than in the common Z., perfectly smooth. 



On sandy shores, usually between liigh- and low-water marks, in various 

 parts of the world. Common in western Europe, and has been found on 

 several points of the British coasts. Fl. summer and auttimn. The seeds 

 appear certainly distinct in the two species ; the constancy of the other 

 characters is doubtful. I have examined only the dwarf species in a living 

 state. 



II. NAIAD. NAIAS. 



Slender, branching, submerged plants, vrith linear, opposite or temate . 

 leaves, often crowded into whorls or clusters, and usually toothed. Flowers 

 small and sessile, often clustered with the branch-leaves in the axUs, and di- 

 oecious or rarely monoecious ; the males consisting of a single, nearly sessile 

 anther, enclosed in a little membranous bract ; the females of a single ovary, 

 sessile in the sheatliing base of the leaf, with 2 to 4 subulate stigmas. Fruit 

 a small, seed-like nut. Embryo straight. 



A genus of few species, widely spread over a great part of the globe. 



1. Slender Naiad. Naias flexilis, Bostk. 



Leaves narrow-linear, usually in whorls of 3, or sometimes opposite, 

 often clustered in the axils, about 6 or 8 lines long ; the teeth few and very 

 minute. Stigmas usually 3, sometimes 4. Fruit oblong, about a line 

 long. 



A common North American species, observed in a few scattered localities 

 in Eui'ope, and recently detected by Mr. D. OUver in Connemara, in Ire- 

 land. Fl. summer. 



III. ZANNICHX:i.I.ZA. ZANNICHELLIA. 



A genus limited to a single species ; difiering from the . narrow-leaved 

 Pott diveeds by the monoecious flowers sessUe in the axils and without peri- 

 anth, from Rwppia in the usually opposite leaves, in the single stamen with 

 a long filament, and in the shape of the fruit. 



