NAIADACEA 2 . (PONDWEED FAMILY.) 457 
New England to Ohio northward_Stems 2° 4° Inn* r 
mZ'co e,3 '" 6 ' )ong ; ii ' ,wide - ™--e,/^: n : rv i7 and tr: 
more conspicuous midrib or 3 nerves, perfectly entire. 
iikl\uYZkr i / <IdrUS ’ PU , ,Sh - Ste “ Vc ^’ s,endcr and thread- 
* ’ J u‘ h ’ haves narTOW, y linear, acutish ; spikes few 14-fi t 
% oZ thI seZ P 7 h V r' etS ° bliqUely Unli ^ distinctly crtl 
ed on the semictrcular back. (P. gramineus, Michx.) - Ponds and 
* earns common especially southward. _ Leaves P-3' long J 
wide, obscurely 3-nerved. Nutlets scarcely 1' long, flattened on thp 
tdes, short-pointed from the inner edge, the back obtusely sinua.t 
toothed on the keel when dry. Nearly allied to the next. ? 
12. P. piisillus, L. Stem slender, obscurely compressed 
leaves narrowly Imear, rather acute, 3-5 -nerved: smkes 4 -H.iT V 
often interrupted, much shorter than the peduncle - nutlets "Utr™/’ 
elliptical (oblong-elliptical, Fries), turgid, obtusely keeled (P 7om 
pressus, ^.) Crooked Lake, New York, Sa!tw£ t Z'ey 
have seen no American specimens of this species. The neufsby 
some deemed a variety of it. 1S Dy 
13. P. tnchoides, Cham., Fries. Stem slender and thread- 
ike, very leafy; leaves capillary, obscurely X-nerved, very acute; spikes 
4 - 8-flowered (long-peduncled) j nutlets half orbicular, JlaUish on the 
aides, m inutely keeled (when dry). - Pond in the Notch of the Whitt 
Mountains, New Hampshire, Robbins, Oakes, Tuckerman. - Stems 1° 
driedTt Tf 2 ' l<>DS ’ a PP earin S entirely capillary when 
dried, but flat under a lens, about i" wide near the base, tapering up 
iTthe last” eXC6SSiVeIy deliC3te point - Nut,ets laf ger and flatter than 
§ 4. Stipules united with the sheathing base of the leaf, scarious: leaves 
all immersed and similar , alternate , grassy-linear. 
J ] ' * >eC , t ™ &ms ’ L - S *eme thread-like, many times fork- 
ed leaves bnstle-form, X-nerved ; spikes interrupted, long-peduncled • 
nutlets rounded-obovate. (P. marinum, L.) Brackish ponds and 
ditches along the coast; also not rare in fresh water, west to YViscon- 
poin7 fTT l0ng : ,hickLsh > tepefing gradually to a slender 
P • usters of the spike 3 or 4, separated in fruit by considerable 
intervals. 
lo. P. Robbinsij, Oakes. Stems sparingly branched, rigid 
'ery leafy; leaves linear, flat, abruptly pointed, many-nerved,serrulate- 
mae; stipules bristle-bearing; “spikes oblong.” — Ponds, not un 
common m New England, detected in 1829 by Dr. Robbins—A very 
ZSK SPCC V eS ;. Stems 10 -^ ,0ng ’ en,ire ‘y invested by the 
nortinn % ° ftbe Ieaves and the eIon S ated and taper-pointed free 
Leaves 3'-4'long h 7° lon g bristles a ® in Polygonum. 
n 8’ ^-4" wide, approximate, strictly 2-ranked, re- 
