VII.] HYDROCHARIDEAi. i6i 



one to three feet high. The flowers secrete honey 

 from twelve glands, situated on each side of the 

 projecting bases of the stamens. These are six in 

 number, and the pollen-covered side of the anthers 

 is, according to H. Miiller, turned outwards. Under 

 these circumstances, insects are more likely to fertilise 

 the flower with pollen obtained from another blossom 

 than with its own. 



In Butomus, on the contrary, the flowers are on 

 stalks, and form a large flat umbel. They are 

 proterandrous ; while Triglochin, according to Axell, 

 is proterogynous. 



HYDROCHARIDEy^;. 



This order contains three British genera ; Elodea, 

 Hydrocharis, and Stratiotes. 



Elodea canadensis {Anacharis Alsinastrnm) is a 

 common American weed, which first appeared in our 

 country in 1847, and has since spread with great 

 rapidity. It is dioecious, and it is remarkable that it 

 has not as yet been known to produce male flowers 

 in this country ; they are, moreover, rare in America. 

 I The female flowers are small, with a long, threadlike, 

 perianth-tube, containing a style which terminates in 

 three stigmas. 



Stratiotes aloides is also dioecious. The male 

 flowers are contained several together in a spathe, 

 stalked, and have twelve or m.ore stamens. The 

 female flowers are solitary and sessile. Both sexes 

 secrete honey. 



M 



