ANGIOSPERMiE, MONOCOTYLEDONES. 



739 



There are 15 species in all. 



Alismacece. — Possess a 6-leaved perianth, and stamens with tendency to increase 

 by division; carpels numerous. Here are included Alisma Plantago, the Water 

 Plantain, and Sagittaria sagittifolia, the Arrowhead. 



There are about 50 species. 

 Butomacece. — Includes Bidomus umbellatus, the Flowering Rush, interesting 

 from the fact that it bears ovules all over the internal surface of its carpels. 



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Fig. 419.— Curled Pondweert (Potamogeton crispus). 



Hydrocharidacece. — Is distinguished from the foregoing families in that it 

 includes submerged forms with inferior ovaries. The flowers are frequently uni- 

 sexual, and in one form (Halophila) are pollinated under water, as in so many of 

 the Potamogetacese. To this family belong Vallisneria (see fig. 155, vol. i. p. 667 

 and fig. 227, p. 132), Elodea, the American Water-weed (alluded to on p. 457), 

 Lagdrosiphon and Enalus (p. 133), Stratiotes aloides, the Water-soldier (vol. i. p. 552) 

 and Hydrocharis Morsus-rance, the Frog-bit, with expanded floating leaves. 

 Contains about 60 species. 



