nYDuocnARinACEA,. 77 



ORDER LXXIX.— H YDROCHARIDACE^. 



Aquatic herbs generally perennial, submerged, or with the upper 

 leaves floating; the flowers rising out of the water, or at least to 

 the surface, at the time of fertilisation. Rootstock with runner-like 

 stolons producing a new plant at their extremity, more rarely sobo- 

 liferous. Leaf-bearing stem undeveloped or elongated and branched. 

 Leaves all radical or opposite or verticillate ; when submerged, pel- 

 lucid, simple, undivided ; when the lamina is stalked it is often 

 cordate at the base; venation generally cancellate. Flowers com- 

 monly dicEcious, rarely polygamous, enclosed in a spathe of 1 to 3 

 bracts while in bud. Male flowers usually several, rarely solitary, 

 enclosed in a 1- or 2-leaved spathe : perianth of 6 (rarely 3) segments ; 

 the 3 outer generally herbaceous ; the 3 inner petaloid, rarely absent : 

 stamens inserted at the bottom of the perianth, 3, 6, 9 or many, some 

 of them frequently sterile ; filaments free or monadelphous ; anthers 

 introrse, rarely extrorse, 2-celled : ovary rudimentary. Female and 

 perfect flowers sohtary, from a tubular spathe : perianth with a tube 

 united to the ovary; limb 6-partite, rarely 3-partite; the 3 outer 

 segments generally herbaceous; the 3 inner petaloid, rarely absent: 

 stamens without anthers, or (in the perfect flowers) with anthers 

 similar to those of the male flowers: ovary inferior, adnate to the 

 tube of the perianth, of 3, 6, or 9 caq^els, and generally of as many 

 cells as carpels, sometimes 1 -celled when there are 3 carpels, and 

 in that case with 3 parietal placenta3; ovules numerous; j^Iacentaj 

 gelatinous, usually on the dissepiments in the multilocular ovaries; 

 styles short or sometimes elongated and connate, with the tube of the 

 perianth as many as the number of the carpels; stigmas entire or 

 2-cleft. Fruit ripening under water, indeliiscent, herbaceous. Seeds 

 numerous, indefinite; testa membranous, very often clothed with 

 spiral fibres ; albumen none ; radicle pointing towards the hilum or 

 away from it. 



GENUS L—B. YDROCHARIS. Linn. 



Flowers dioecious. Male flowers usually 3 in an umbel, pedicellate 

 from a 2-leaved membranous spathe supported on a scape: perianth of 

 6 leaves, the 3 outer leaves oval, subherbaceous ; the 3 inner larger, 

 suborbicular, and petaloid : stamens 12 ; filaments united at the 

 base, forked at the apex, 9 only (or more rarely 6) of them with 

 anthers which are attached to the posterior fork of tho filament: ovaiy 



