76 NAIADACEAE. 



28. Potamogeton gemmiparus (Robbins) Morong. 



(Fig. 169.) 



Pola mogeton pu stilus var. ( ? ) gem m ipa rus Rob- 

 bins in A. Gray, Man. Ed. 5, 489. 1867. 



Potamogeton gemmiparus Morong, Coult. Bot. 

 Gaz. 5: 51. 1880. 



Stems filiform, terete, branching, s / -4 

 long. Leaves capillary, sometimes not as 

 wide as the stem, often with no perceptible 

 midrib, tapering to the finest point, I'-tf 

 long, 2-glandular at the base ; stipules J^'-i' 

 long, acute or obtuse, mostly deciduous ; 

 spikes interrupted, 3-6-flowered ; peduncles 

 filiform or sometimes slightly thickened, 

 #'-2' long ; fruit seldom formed, similar to 

 that of P. pusillus, except that it is flatter 

 and somewhat impressed on the sides. 



In ponds, eastern Massachusetts and Rhode 

 Island. It is commonly propagated by its abun- 

 dant buds, the leaves and stems are often alike 

 in thickness so that the plant seems to consist 

 of threads. Aug.-Sept 



Capillary Pondweed, 



29. Potamogeton diversifolius Raf. Rafinesque's Pondweed. (Fig. 



Potamogeton hybridus Michx. Fl. Bor. Am. i: 

 101. 1803. Not Thuill. 1790. 



Potamogeton diversifolius Raf. Med. Rep. (II. > 

 5 : 354. 1808. 



Stems flattened or sometimes terete, much 

 branched. Floating leaves coriaceous, the 

 largest i' long by ^' wide, oval or elliptic 

 and obtuse, or lanceolate-oblong and acute \. 

 petioles generally shorter, but sometimes 

 longer than the blades, filiform or dilated ; 

 submerged leaves setaceous, seldom over 

 X" wide, i '-3' long ; stipules obtuse or trun- 

 cate, $"-5" long, those of the floating leaves 

 free, those of the submerged leaves some- 

 times adnate ; emersed peduncles $"-~" 

 / "^ ^^^^J I \ lon g; submerged peduncles 2 // -3 // long, 



4 / / K%Z\lh4^ \ clavate, as long as the spikes ; emersed spikes- 



3 "-5" long, occasionally interrupted ; fruit 

 cochleate, rarely over y t " long, 3-keeled, 

 the middle keel narrowly winged and usu- 

 ally with 7 or 8 knob-like teeth on the mar- 

 gin, the lateral keels sharp or rounded ;. 

 embryo coiled i^ times. 



In still w.iu-r. Miine to Florida, west to Nebraska and Texas. June-Sept. 



Potamogeton diversifolius multidenticulatus Morong, Mem. Torr. Club, 3: Part 2, 48. 1893. 

 Differs from tin- typt- in the numerous teeth of the fruit, as many as 12 being sometimes found 

 le keel, and each lateral keel with 6-8 more, the teeth often bristle-like and sometimes 

 a-I>riiifc<l. Connecticut to eastern Pennsylvania and Delaware. 



Potamogeton diversif61ius trichophyllus Morong, Mem. Torr. Club, 3: part 2, 49. 1893. 



Plant alx.ut 6' long, without floating leaves, the submerged leaves as fine as floss silk and: 

 entirely nerveless. Lake Marcia, New Jersey. 



