Eo 
230 E.. Tuckerman on New England Plants. 
ris plus minus reversis, natantis cylindricis plurifloris pedunculis 
longiusculis; fructibus recentibus oblique lunato-lentiformibus 
compressis tricarinatis, stigmate faciali sessili, dorso deorsum eur- 
vato anguste alato-carinato dentato, carinis lateralibus acutinscu- 
yp AD herb. ! 
Has. Small ponds and plashes; Cambridge, Plymouth, 
er side, one-nerved, 1-3 inches long. Floating leaves 
subcoriaceous, a little more oval than in the last, furrowed on the 
under side with 3-7 impressed nerves, 6-10 lines long by 3-4 
wide, on rather flat petioles which are free from the strongly 
nerved stipules. Peduncles longer than in the last, more or less re- 
versed in fruit. Nutlets minute, half the size of those of the last, _ 
very oblique, rounded, compressed, tricarinate, the back narrowly 
alate, with 6~8 approximate teeth, the lateral keels acute, and of- 
ten sinuate-toothed when dry, the sides obsoletely eochleate-sul- 
cate. Exocarp very thin, alittle produced on the back. Putamen 
semi-transparent. Seed cochleate. This species, P. Spiritlus, and 
P. Claytonii are peculiar to this country, and, at first sight, are not 
easily referred to either of the commonly received sections of 
the genus. They differ from the Heterophylli or Diversifolii of 
authors in ch ters much more important than the solitary one 
(the floating leaves) in which they are considered to agree with 
them, and shew, as it seems to me, very clearly, that this group 
cannot be retained in arranging the North American species. P 
Claytonii belongs to the Graminifolii, irrespectively of its coria- 
ceous leaves, and the two.others mentioned, if they accord with 
the Heterophylli in their floating leaves, accord at the same time 
with the Graminifolii in their submersed leaves and inflorescence, 
and with the Vaginiferi or ColeophyHi in the attachment of their 
leaves to the stipules. This last character is not easily noticeable 
in P. hybridus, and seems to have escaped attention, but it is 
conspicuous in the nearly allied P. Spirillus. . The arrangement 
proposed by Fries (Novitie, edit. 2, p. 27) for the Swedish Po- 
tamogetons, admitting two principal sections, I, of these with 
submersed leaves broader in the middle (Plantaginifolii; in 
which the Natantes or species with simple stems constitute the 
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