50 BOTANICAL GAZETTE. 



New Species of Potamogeton, with notes upon some published 

 FORMS. — Owing to the difficulty of obtaining specimens of certain 

 European species in fruit which are needed for comparison and safe 

 determination, the writer has been unable hitherto to complete the 

 promised revision of the North American species of Potamogeton. 

 The following notes are published in advance in the hope that they 

 may prove of service to collecting botanists during the coming season, 

 and for the purpose of soliciting further specimens. The determina- 

 tions of new species here offered are not regarded as final. 



P. Illinoensis. — Stem stout, branching towards the summit ; float- 

 ing leaves opposite, thick, coriaceous, oval or ovate, 2-3 inches long 

 hy i}4 broad, 19-23 nerved, rounded or sub-cordate at base, and 

 with a short blunt pointat the apex, on short petioles: submerged leaves 

 comparatively few, dark green, oblong-elliptical, acute at each end, 

 usually ample (the largest nearly 8 inches long and i}4 wide), entire, 

 rarely mucronate, nearly or quite sessile, the uppermost opposite; 

 stipules coarse, free, obtuse, strongly bicarinate, about 2 inches in 

 length; peduncles often clustered at the summit of the stem, 2-4 inches 

 long, usually somewhat thickening upwards ; spikes about 2 inches 

 long, densely flowered; fruit roundish obovate, 1^-2 lines long and 

 i-i^ lines wide, 3-keeled on the back, the middle keel prominent 

 and sometimes shouldered at the top, flattened and slightly impressed 

 on the sides, obtuse or occasionally pointed at the base, the style 

 short and nearly facial, the apex of the embryo pointing transversely 

 inwards. 



Allied to F. lucens, L., in habit, but with larger fruit, and in foliage 

 quite distinct. It was first discovered by Mr. H. N. Patterson in the 

 Mississippi River bottoms, near Oquawka, 111. Apparently the same 

 is also sent by Rev. E. J. Hill, collected in ditches at Englewood, 111 , 

 but his specimens approach the luccns type more nearly, having very 

 large oval, shining upper submerged leaves, which (as also the float- 

 ing) are 23-38 nerved. 



P. Mysticus. — The whole plant very slender; stems irregularly 

 branching, from a creeping rootstock, nearly filiform, terete, 1-3 feet 

 high; leaves all submerged, scattered, entire, oblong-linear, ^-i}^ 

 inches long and 2 or 3 lines wide, 5-7 nerved, finely undulate, obtuse 

 or bluntly pointed at the apex, abruptly narrowing at the base, and 

 sessile or partly clasping ; stipules free, obtuse, about 6 lines long, 

 mostly deciduous but often persistent and closely sheathing the stem; 

 spikes few, capitate, 4-6 flowered, on erect peduncles from i to 2 

 inches in length. Fruit fully matured not seen, but one or two rather 

 immature specimens indicate that it is obovate, minute, scarcely ^ of 

 a line long by ^ a line broad, obscurely 3-keeled on the back, a lit- 

 tle beaked by the slender, recurved style. 



With the habit of P. perfoliatus, but scarcely one-third as stout in 

 any of its parts. — Aug., Sept. Mystic Pond, Medford, Mass., the 

 sheet of water in which the early American investigators of this ge- 

 nus found so many of their plants. The author was not aware that 



