28 MISSOURI BOTANICAL GARDEN. 
did Dr. Engelmann examine the material preserved in all of 
the principal American herbaria, but in his visits to Europe 
in 1856-7, and 1883, he studied the types and American 
collections preserved in the great English and Continental 
herbaria. These notes and the types in his own very rich 
herbarium have served as a foundation for the work 
undertaken. 
I have followed Buchenau and Micheli in separating the 
species of Lophotocarpus from Sagittaria. Lophotocar- 
pus is annual (at least our species), the flowers are perfect 
or staminate, and the stamens are hypogynous. Sagittaria is 
perennial, monoecious or dioecious with the fertile flowers 
never perfect, and the stamens are borne above the recepta- 
cle. The separation of Lophotocarpus simplifies the genus 
Sagittaria very much, reducing somewhat its cosmopolitan 
character. In their present form the genera more nearly 
express the genetic relationship. 
Sagittaria is a genus consisting of from ten to thirty 
species, according as the ideas of the various monographers 
differ. A large part are American, the rest extending over 
Europe and Northern Asia. Of the twenty-two species 
which I have recognized in North America, one is only an 
introduced ballast plant, and one extends into Central and 
South America. 
The American S. latifolia, together with the related 
species of the group Sagittifoliae, has been considered as 
falling within the limits of the widely distributed European 
and Asiatic S. sagittifolia. Micheli, in DC. Monog. Phan. 
3: 66, 69, and, following him, a number of American sys- 
tematists, have held this opinion. Dr. Engelmann, in A. 
Gray, Man. Ed. 2 (1856), first pointed out the differences 
which separate the two species. Buchenau, in Engler, Bot. 
Jahrb. 2: 486 (1882), supports this view that they are 
distinct. In this I have followed Engelmann and Buchenau. 
The two species occupy different geographical ranges and 
are isolated one from the other, although both undoubtedly 
derived from the same stock. The American species are 
2 
