1917] ~~ Fernald,— Elatine in eastern North America 11 
might be the same as Pursh’s Peplis americana but which is appar- 
ently quite distinct from Pursh’s plant, although commonly occurring 
in fresh sandy and gravelly shores, occasionally extends into wet 
clay and even into the borders of salt marshes, although it is apparently 
rare in these extreme habitats. 
The plant which is more distinctive of brackish or tidal mud, the 
plant with petioled obovate leaves, has a trimerous flower, with three 
sepals and three petals, and is undoubtedly the plant intended by Pursh 
as his Peplis americana, which was described, “foliis crassis spathu- 
lato-obovatis’’, and which was “inundated during its flowering time, 
in slow-flowing places of rivers, in Pensylvania.”! The habitat, it 
is true, is so similar to that of Nuttall’s later published Crypta minima 
that it was quite natural for Nuttall to assume that his plant and 
Pursh’s were identical, but Nuttall’s species had dimerous flowers, 
while Pursh’s plant of inundated shores was put by him into the Lin- 
nean group Hexandria, where he certainly would not have placed a 
plant with dimerous flowers. 
The plant with petioled obovate leaves, which occurs on the tidal 
flats of Cathance River in Maine and on the tidal flats of the Dela- 
ware, as well as at a few other stations along the Atlantic coast, has 
very definitely three sepals and three petals, although the writer has 
been unable to determine with complete satisfaction (owing to the 
maturity of specimens) whether the stamens are three or six. In view, 
however, of the occurrence of this plant with trimerous flowers and 
obovate leaves on the tidal flats of the Delaware River, there is little 
doubt that it is the plant intended by Pursh as Peplis americana. 
This plant, which is identified with Pursh’s species and which was 
afterwards called Elatine americana by Arnott, differs from Crypta 
minima (Nuttall) Fischer & Meyer in having the seeds ordinarily 
curved and decidedly more slender, ranging from 140-190 yu in diam- 
eter and with the longitudinal ribs much more irregular and obscure 
and connected by 20-30 acute cross-ribs. 
The third plant of the Atlantic slope is a well known species of 
Europe, E. triandra Schkuhr, which has the trimerous flowers and 
essentially the seed of true E. americana but which has thin linear, 
elongate-lanceolate or lance-spatulate, often toothed leaves, and 
which often grows to a height of 2 dm. with long internodes, in these 
1 Pursh, Fl. Am, Sept. i. 238 (1814). 
