Damasonivm.] LXXIX. ALISMACE^l. 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. ^fig. 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. HYDROCHAEIDE^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-ube short, on a slender pedicel. Stigmas 6 . .2. HTDROOHARI3. 



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



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



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 lontr, so as to attain the 



2s 



