30. 



PONDWEED FAMILY. 



Spiral Pondweed. 



77 



Potamogeton Spirillus Tuckerm. 



Sf>iri I Ins Tuckerm. Am. Journ. Sci. 

 11)6: 228. 1848. 



Stems compressed, branched, 6'-2o' long, the 

 branches often short and recurved. Floating leaves 

 -oval or elliptic, obtuse, the largest about i' long 

 and Yz' wide, with 5-13 nerves deeply impressed 

 beneath, their petioles often i' long ; submerged 

 leaves linear, \y 2 "-2" long, about y^" wide, mostly 

 5-nerved ; stipules of the upper floating leaves free ; 

 those of the submerged leaves adnatc to the blade 

 or petiole ; spikes above water 3 // ~5 // long, contin- 

 uous, the lower mostly sessile, capitate and i-io- 

 fruited ; fruit cochleate, roundish, less than i" 

 long, flat and deeply impressed on the sides, 3- 

 keeled on the back, the middle keel winged and 

 sometimes 4-5 -toothed ; style deciduous; embryo 

 spiral, about i^ turns. 



In ponds and ditches, Nova Scotia and Ontario to 

 Minnesota, south to Virginia, Missouri and Nebraska. 

 June-Aug. 



31. Potamogeton filifdrmis IVrs. Fili- 

 form Pondweed. ( Fig. i 



Potamogelonfiliformis PITS. Syn i 152. 1805. 



Stems from a running rootstock, slender, 3- 

 long, filiform above, stout and thick towards the 

 base. Leaves numerous, a'-ia' long, %" 

 wide, i -nerved with a few cross veins ; sheaths 

 about i" long and the free part of the stipule #' 

 long, scarious on the edges ; flowers on long, often 

 recurved peduncles, 2-12 in each whorl, the whorls 

 X'-i' apart ; fruit i"-i#" long, slightly less than 

 \" wide, the sides even, the back not keeled, the 

 face nearly straight or obtusely angled near the 

 top ; stigma nearly or quite sessile, remaining on 

 the fruit as a broad truncate projection. 



In ponds and lakes, Anticosti to western New \ 



and Michigan. August. 



Potamogeton filiformis Macounii Morong; Macoun, Cat. Can. PI. 4: 88. 188! 

 Leaves i'~3' long, the largest Vt" or more wide, obtuse, stiff, with a -tri>nn midrib and raised 

 or'slightly revolute margins; fruit rarely more than i" long; peduncles oti long; plant 



commonly with a compact bushy habit. In brackish or salt water lakes, praine region of Canada, 



.32. Potamogeton pectinatus L,. Fennel- 

 leaved Pondweed. (Fig. 173.) 



Potamogeton pectinatus L- Sp. PI. 127. 1753. 



Stems slender, much branched, i-3 long, the 

 branches repeatedly forking. Leaves setaceous, 

 attenuate to the apex, i-nerved, i f -6' long, often 

 capillary and nerveless ; stipules half free, %'-*' 

 long, their sheaths scarious on the margins ; pe- 

 duncles filiform, 2 / -i2 / long, the flowers in verti- 

 cils ; fruit obliquely obovoid, with a hard thick 

 shell, i ^"-2" long, i"-iX" wide, without a mid- 

 dle keel, but with obscure lateral ridges on the 

 back, plump on the sides and curved or occasion- 

 ally a little angled on the face ; style straight or 

 recurved, facial ; embryo apex pointing almost 

 directly toward the basal end. 



In fresh, brackish or salt water, Cape Breton to Brit- 

 ish Columbia, south to Florida, Texas and California. 

 Also in Europe. July-Aug. 



