MANUAL OF NATURAL HISTORY. 501 



unisexual ; perianth 6-divided, in two whorls, 

 inner whorl petaloid; stamens definite or 00; 

 anthers introrse ; ovaries several; ovules soli- 

 tary or in pairs ; placentae axile or basal ; 

 fruit dry, 1-2-seeded; embryo curved or 

 hooked. Floating or marsh plants, chiefly 

 in northern temperate regions. 

 3. FAMILY. Flowering-rushes (Butomacese). Her- 

 baceous ; often lactescent ; leaves very cel- 

 lular ; flowers umbellate or solitary, conspi- 

 cuous ; perianth 6-divided, in two whorls, 

 the outer herbaceous, the inner petaloid ; 

 stamens definite or 00 ; ovaries 3-6, or more, 

 united or distinct; ovules 00, anatropal or 

 campylotropal ; placentae many-seeded, net- 

 ted, and parietal ; fruit of several follicles, 

 distinct and beaked, or united ; embryo often 

 curved. Aquatic and swamp plants, mostly 

 northern. 



II. ORDER LILIALS (Liliales). 

 Perianth 6-divided ; albumen copious. 

 1. FAMILY. Pontederiads (Pontederiacese). Herba- 

 ceous ; leaves sheathing, sometimes cordate 

 or sagittate ; flowers solitary, or in spikes or 

 umbels, spathaceous ; perianth tubular, co- 

 loured, circinnate when withering ; stamens 

 3-6 ; anthers introrse ; ovary free, 3-celled ; 

 ovules numerous, anatropal ; fruit capsular, 

 3-celled, 3-valved; seeds 00; embryo straight; 

 albumen mealy. Aquatic species, inhabiting 



