Notes on North American Haloragese. 



By Thomas Morong. 



The order Haloragece consists mostly of aquatic plants, and, 

 as arranged by Bentham and Hooker, comprises nine genera, 

 four of which occur in northern North America and one other in 

 southern Mexico. These genera differ widely from each other in 

 some important points, but so far as the structure of the ovules 

 and embryos is concerned, form a very natural family. The 

 Order was formerly classed by most botanists with the Onagraceae, 

 and in some botanical works many of the genera are still retained 

 in that family, but they evidently differ radically from the mem- 

 bers of that Order in nearly all the essential ordinal character- 

 istics. Ceratophylhim was included among the Haloragece by 

 Bentham in his Flora Australiensis, but probably by mistake, 

 as the peculiar embryo, the four verticillate cotyledons and the 

 exalbuminous ovules of CeratopJiylhmi absolutely forbid its intro- 

 duction into this group of plants. Curiously enough, too, 

 Bentham's own ordinal description debars this genus from a place 

 here. 



The only objection to the arrangement of Bentham and 

 Hooker which is likely to be made is in regard to the position of 

 Callitriche, which has commonly been regarded as unique and 

 as constituting an Order by itself Upon a careful examination, 

 however, it cannot be doubted that in habit, in its four-carpelled 

 fruit, its ovules and embryos, this genus bears a very close rela- 

 tionship to MyriopJiyllum, while in the stamens and styles it 

 strikingly resembles Hippuris, especially those forms of H 



