Damasonivm.] LXXIX. ALISMACE^E. 433 



IV. DAMASONIUM. DAMASONIUM. 



Herbs, only differing from Alisma in the carpels, which are few, larger, 

 usually 2-seeded, and cohere by the base to the central axis of the flower. 



Besides the European species, the genus comprises two others from 

 Australia and California. 



1. D. stellatum, Pers. ifig. 977). Star D.A. tufted, glabrous 

 annual Leaves all radical, on long stalks, ovate or oblong, often cor- 

 date at the base. Flower-stems erect, from 3 to 9 inches high, usually 

 bearing 1 terminal umbel, and 1 to 3 whorls of rather small flowers 

 lower down. Inner segments of the perianth very delicate, white, with 

 a yellow spot at the base. Carpels 6, tapering into a long point, and 

 radiating horizontally, like a star. Actinocarpus Damasonium, Br. 



In watery ditches, and pools, in western and southern Europe, and 

 west-central Asia, but not extending into Germany or Scandinavia. In 

 Britain, only in some of the southern and eastern counties of England. 

 Fl. summer. 



LXXX. HYDROCHARIDE.E. HYDROCHARIS FAMILY. 



Aquatic herbs, with undivided leaves, and mostly dioecious 

 flowers, enclosed when young in an involucre or spatha of 1 to 

 3 leaves or bracts. Perianth of 3 or 6 segments, either all petal- 

 like or the 3 outer ones smaller and herbaceous, with a tube 

 adherent to the ovary at its base in the females, without any 

 tube in the males. Stamens in the males 3 to 12. Ovary in 

 the females inferior, 1-celled, with 3 parietal placentas, or divided 

 into 3, 6, or 9 cells. Styles 3, 6, or 9, with entire or 2-cleft 

 stigmas. Fruit small, ripening under water, indehiscent. Seeds 

 several, without albumen. 



A small Order, widely diffused over the globe. 



Stem floating and branched, with small opposite or whorled 

 leaves. Female perianth-tube long and thread-like. Stig- 

 mas 3 1. ELODEA. 



Stem root-like, with floating tufts of orbicular leaves. Female 



perianth-tube short, on a slender pedicel Stigmas 6 . .2. HYDROCHARIS. 



Stem scarcely any. Leaves tufted, succulent, radical. Female 



perianth-tube short, on a stout pedicel Stigmas 6 . 3. STRATIOTES. 



I. ELODEA. ELODEA. 



Stems submerged, branched and leafy. Flowers sessile, the males 

 with 3-9 stamens, the females with a long, thread-like perianth-tube. 

 Style adherent to the tube, with 3 notched or lobed stigmas. Ovary 1- 

 celled, with 3 parietal placentas. 



A small genus, temperate and tropical 



1. E. canadensis, Michx. (fig. 978). Water-thyme. A dark green, 

 much branched submerged perennial. Leaves numerous, opposite or in 

 whorls of 3 or 4, sessile, linear-oblong, transparent, 3 or 4 lines long. 

 Flowers sessile in the upper axils, in a small, 2-lobed spatha ; the slender 

 perianth-tube of the female often 2 or 3 inches lonf, so as to attain the 



