ee ae 
a 
a 
us. Salix Mahlenbergian, (115. Salve longifolia, Muhl 
(102) Mr. tae Plants of Iilinois and Missouri. 
jeer la cae “Wil Willd./1 16. Salix _ Muhl. ?. 
Gu ee Higra, ‘Marsh? 
Ail; 117. Potamndgeton Tvepioling, Barton, °. spicatus. This form 
appears at fifst view to be a distinct speci species, characterized by the 
narrower, only 5-nerved upper leaves, and petioled oval or cylin- 
dric spikes. P. diversifolius, «. capitatus, the common form, h 
more oval 7-nerved upper leaves, and nearly sessile few-flower 
heads. But sometimes the lower heads of our variety are al 
capitate and nearly sessile, and the fruit is generally alike. 
fruit, or nut, is always compressed, winged on the back, with tw 
ateral carinee, which are generally denticulate, the nut appearin 
muricate ; and in #. they are often nearly or entirely undivided, 
but by no means generally so. The embryo describes 13 of-a 
spiral circumvolution ; the embryo of most other species fo 
only 2, 1 or 14 circumvolution. I know but one species, | 
densus, which exhibits 24 circumvolutions. . 
It may not be amiss here to remind botanists in this countr 
that the ripe fruit furnishes the best characteristic marks to di 
tinguish the different species of Potamogeton. The fruit, for e 
ample, proves that P. marinus, Linn. is entirely distinct from P. 
pectinatus, Linn., with which most authors confound it; P. ma- 
rinus occurs not only on the sea-coast, but also in the saltspod 
of the Upper Missouri, (Geyer, in Nicollet’s expedition.) Spec 
mens of Potamogetor: should always be collected with bhi fruit. 
118...Phalangium esculentum, Nutt. 5 
ALY. pels recurvatum, Beck. 
ds 
x s | ichi in 49 : Perm 
cae wor rus Fallindoes, Vahi-> 
+123. Isolepis capillatis, Rem! & Sehult> 
424, Heléocharis tenuis, “Sehiult: 
: 425. See gracile, Koch, in Roth. catalect, 2. p. 2 
A ipétien ich has ficihenty been: found in the United Stasi 
it appears to have been taken for E. anguslifolium—my speci 
mens at Teast, received from Pennsylvania and from Ohio, w 
so. fabelled—but is easily distinguished by its triquetrous, sub 
leaves, snd the linear yellowish seeds. The true E. angu. 
lium, Roth, is the largest of all the species, with the lon 
a pases mer leaves 1 or te lines broad, channeled; [ 
