II.] KEY TO NATURAL ORDERS. 145 



coloured flowers. Stamens three. Ovary inferior, three- 

 celled. 



HYDRocHARiDACEiE (p. 329). — Submerged or floating 

 herbs. Flowers usually unisexual. Perianth three- to six- 

 leaved. Ovary inferior. Seeds exalbuminous. 



Alismace/e (p. 331). — Aquatic herbs. Perianth free, siy- 

 leaved ; three inner leaves petaloid. Pistil apocarpor.s. 

 Seeds exalbuminous. 



NAiADACEiE (p. 332). — Floating or submerged herbs. 

 Perianth minute, four-leaved or o. Stamens one, two, or tour. 

 Ovary free, of one, two, or four distinct carpels. Seed 

 exalbuminous. 



CvPERACEiE (p. 333). — Grass-like herbs. Sheaths of the 

 leaves entire (not split). Flowers hermaphrodite or uni- 

 sexual, naked or perianth reduced to bristles ; each in the 

 axil of a single scaly bract. Embryo at the base of copious 

 albumen. 



GRAMiNEiE (p. 335). — Grasses. Herbs (except in Bam- 

 busa and aUies). Sheaths of the leaves usually split. 

 Flowers usually perfect, sheathed by two-rowed scaly 

 bracts (glumes), of which the innermost (pale) is usually 

 two-nerve4. Embryo obliquely applied at the base of 

 copious albumen. 



