Remarks on the Genera Callitriche and Elatine. 43} 
Accurately figured by Lamarck, Ill. Tab. 320, f. 2. In this 
species the calyx.is only quadrifid, and not divided to the base ; 
the lobes are so very broadly ovate as to be almost orbicular. 
3. E. hexandra ; leaves opposite; flowers alternate, on peduncles 
about the length of the leaves, mith six stamens and three petals ; 
calycine segments spreading. | 
I have not observed this to vary in the number of the parts of 
the flower, though I think it extremely probable. It is a much 
smaller and-more delicate plant than the last, and the calyx is 
much more deeply divided. When growing in a muddy and nearly 
dry situation, the upper surface of the leaves becomes very visibly 
rough with minute dots, as described by Smith; but when in 
water, the leaves are as smooth as in EL. hydropiper: the leaves 
are rather more attenuated at the base into a petiol than in the last. 
. hydropiper seems to be by much the least common of the two ; 
I only have it from the neighbourhood of Paris: but E. hexandra 
I have from Paris, Fontainbleau, Strasburg, Gentoud, and Bur- 
gundy. 
4. E. nodosa, Nob. leaves opposite, oblong, very much attenuated 
. at the base; flowers sessile alternate, with eight stamens and four 
petals ; calyx deeply divided, segments patent. 
This species, readily distinguished by its sessile alternate flowers, 
(in one’specimen only have I seen one instance of the flowers be- 
ing opposite,) is figured, I feel certain, by Schkuhr for the true 
E. hydropiper. It is, however, as slender as the last species. I 
have it from the neighbourhood of Strasburg, and from Nice. 
§ 2. Stamens equal in number to the petals. : 
5. E. triandra, leaves opposite, oblong, attenuated at the base ; 
flowers sessile, opposite, with three stamens and petals; calycine 
segments two.. 
6. E. Americana, Nob. leaves opposite, oval; flowers sessile, al- 
ternate, with from two to three stamens and petals; calyx two 
leaved, (Crypta minima, Nutt.) 
Nuttal, in a work to which I have no access at present, states 
this, as far as I recollect, to have the flowers sometimes opposite ; 
but, in all the specimens I possess, they are decidedly alternate. 
In the short oval shape of the leaf it resembles more E. alsinastrum 
than the other species. This is usually supposed to be Peplis 
americana of Pursh. 
As to the natural affinities of this curious genus, placed by De 
Candolle with (?), and by Mr. Lindley, with certainty, among the 
Caryophyliew, I shall say nothing at present: in the seed there is 
no albumen, but a long cylindrical erect embryo, with short cotyle- 
dons and a long radicle, which is inferior, and points towards the 
hilum : it has lately been made the type of a new order, including 
Bergia and a South American genus, by Cambessedes in the Mem. 
du Musée ; but I am not inclined to go with him into many of the 
ideas he has there expressed. 
