FROG-BIT FAMILY 457 



or bast, the vessels being grouped in scattered bundles which 

 are most numerous near the outside of the stem, which, in con- 

 sequence, is hardest near the exterior and sonT,etimes hollow in the 

 centre, especially among the Grasses. The leaves are generally 

 simple, entire, and smooth, with parallel veins, or a regular net- 

 work formed by transverse veins which are much finer than the 

 longitudinal ones. The flowers are often destitute of a perianth, 

 the place of which is supplied by hard, chaffy scales known as 

 glumes. '1 he sepals and petals, when present, the stamens and the 

 earpels are generall)- 3, or some multiple of 3, in number. 



Sub-Class I. PETALOIDE.T; 



Flowers usually furnished with a petaloid and coloured, not a 

 green or glumaceous, perianth. 



Series I. EriGYN.4':.— Ord. LXXVIL— LXXXI 



Perianth superior ; ovary inferior 



Ord. LXX\TI. Hvdrochari'pe.e. — The Frog-eit Fajiilv 



A small Order of aquatic plants, often floating, with con- 

 spicuous, polysymmelric, dicecious floiKers, enclosed, when in bud, 

 in a sheath, or spaihe ; sepals 3, green ; petals 3 ; stamens 3 — 12 ; 

 carpels 3 — 6, united into an inferior, i- or many-chambered OT'ary ; 

 slvlc I ; stigmas 3 — g ; jniit indehiscent, generally a berry, i- or 

 many-chambered. Only three members of the Order occur in 

 Britain, belonging to three different genera. 



*t. Elodea. — Leaves submerged, linear, wliorled. 



2. Hydrociiaris. — Leaves orbicular, floating. 



3. StratkJies. — /.fflzr.T submerged ; sword-shaped, serrate. 



^"r. Elodea c.vNADiiN'sis (American \\'ater-weed, \Vater-th)me). 

 — A submerged, dark-green, translucent plant, with a long, slender, 

 branching, brittle stem, rooting at its nodes ; leaves in whorls 

 of 3, linear-oblong, finely serrate ; floicers floating, small, pink, 

 dii:ecious, only the carpellate form commonly occurring, which 

 has a very slender perianth-tube 4 — S in. long ; 3 sepals : 3 petals ; 

 3 staininodes ; ovary i-chambered ; style slender ; stigmas 3, 

 iigulate.' — Rivers, canals, and ponds ; common. Introduced 

 from America between 1S36 and rS4i. (Name from the Greek 

 helodes, swampy.) 



2. HvDRiicHARi.s (Frog-bit), represented only by the one 

 species H. Morsus-rdncs, a floating plant with creeping stems; 

 roundish, cordate, stalked, floating leaves : and delicate white 



