SPECIES AND VARIETIKS. 321 



tljen sinks again. — Lakes and ditches; common in the fens 

 of the eastern counties. Fl. July. 



(275) Hydrocharis. Frogbit. 



H. Morsus-ranse : aquatic ; stems floating, runner-like, 

 with tufts of thick, entire, stalked, orhicular-cordate leaves ; 

 flowers dioecious : the males on short peduncles, bearing 2-3 

 flowers on long pedicels, enclosed at the base in a spathe of two 

 thin bracts, each flower with the outer segments pale-green, 

 the inner ones large white, and having 3-12 stamens ; the fe- 

 males resembling the males, but with the spathe sessile among 

 the leaves, and the flowers with six styles having 2-cleft stig- 

 mas. — Ditches and ponds. Fl. July, August. 



(276) Anacharis. 



A. Alsinastrum : aquatic, dark-green, much-branched, en- 

 tirely floating under water; leaves numerous, opposite or in 

 whorls of 3-4, sessile, linear-oblong, transparent ; female 

 flowers, the only ones known in this country, sessile in the 

 upper axils, the slender perianth-tube elongated, so as to 

 reach the surface of the water, where it terminates in 3-6 

 small spreading segments. — Ponds, canals, and slow streams, 

 in which it spreads so rapidly as to choke up the channels ; 

 recently introduced from North America. Fl. July to Sep- 

 tember. 



(277) Iris. Flag. 



I. Pseudacorus : aquatic ; stem two feet high ; leaves sword- 

 shaped, the lower ones longer, stiff* and erect, glaucous-green ; 

 flowers 2-3, large, erect, bright yellow, the outer perianth - 

 segments spreading, broadly ovate, clawed, the inner oblong, 



Y 



