212 



MANUAL OF BOTANY 



northern parts of the world. Illustrative Genera: — Butomus, 

 Tourn. ; Lhnnocharis, H. et B. There are 7 species. 



Properties and Uses. — Of little importance. Butomusumhel- 



latus, the Flowering Rush, 



Fig. 978. 



Fig. 979. 



possesses acrid and bitter 

 properties, and was at one 

 time used in medicine. The 

 roasted rhizomes are edible. 

 Order 33. Naiad ace^, 

 the Pondweed Order. — C h a- 

 r a c t e r. — Aquatic plants 

 with jointed cellular stems. 

 Leaves with interpetiolar 

 membranous stipules. 



Flowers small, unisexual 

 (Jigs. 980 and 981), monoe- 

 cious or dicecious, solitary 

 or in spikes. Perianth either wanting, or present and com- 

 posed of 2 or 4 parts, which are then free and scale-like. 

 Stamens 1 or few, hypogynous ; pollen globose or tubular. 



Fig. 978. A flower of the Flowering Rush 

 {Butomus umbeUalus), with au iuferior 

 lieriauth arranged in two whorls, nine 



stamens, and six carpels. Fig. 979. 



Vertical section of the seed of the same. 



Fig. 980. 



Fig. 981. 



Fig. 982. 



Fig. 983. 



Fig. 980. Two flowers of the Horned Pondweed (ZannidielUa palustns), one 



staminate, the other pistillate. /';>/. 981. The gyncecium of the same, 



composed of four perfect carpels, and one imperfect. Fig. 9!52. Vertical 



section of one of the carpels. Fig. 983. Vertical section of the fruit and 



seed. All magnified. After Lindley. 



Carpels 1 or more, distinct, with superior ovaries {fig. 981) ; 

 ovule solitary (». 982). Fruit 1-celled, 1-seeded {fig. 983). 

 Seed exalbuminous ; embryo with a lateral cleft. 



