270 



PETALOTDE.^, 



small, and only two arc natives ot Britain. A species of com- 

 paratively recent introduction is Anacharis Alsinastrum, a sub- 

 merged aquatic, having much the habit of Potamogeton densiis, 

 from which it may be at once distinguished by bearing its leaves 

 three and sometimes four in a whorl. It increases so rapidly that 

 in some places it has seriously impeded canal navigation, and it is 

 a troublesome pond weed. It is a native of North America, but 

 how it was introduced into this country is unknown. 



An.\charis Alsinastrum 



HYDROCnARIS MORSUS-RAN.E 



(Frog-bit) 



1. Hydrochaeis (Frog-bit). — Stamens and pistils on different 

 plants ; stamens 9-12 ; ovary 6-cellcd ; stigmas 6. (Name from 

 the Greek, hydor, water, and charis, elegance, the plants being 

 showy aquatics.) 



2. Stratiotes (Water-soldier). — Stamens and pistils on different 

 ])lants ; stamens about 12, surrounded by many imperfect ones ; 

 ovary 6-celIed ; stigmas 6. (Name, the Greek for a soldier, from 

 its rigid, prickly, sword-shaped leaves.) 



I. Hydrocharis (Frog-bit) 



I. H. Morstis-rancB (Frog-bit).— The only British species. A 

 floating aquatic, with creeping stems, roundish stalked leaves, and 

 delicate white flowers, which grow 2 or 3 together from a pellucid 

 2-leaved sheath. Ponds and ditches ; not general. — Fl. July, 

 August. Perennial, 



