ON POTAMOGETONS. 229 



cfr. Prahl Krifc. Fl. Sell. & Hoi. p. 205 (1880). P. spathulatas 



Kirschlerger, Stat. Veg. Strasbourg. (1845), belongs to /hit'tans ; = 

 P. fitftoti* F. Schultz, Arch. Fr. et All. 61 (1812). A specimen 

 named as Schrader's plant (in herb. A. Brauu), and gathered by 

 Billot, is evidently not so, but belongs to jluitans. An authentic 

 specimen of the original plant (Herb. Mertens), ex herb. Buchenau, 

 shows that this plant must be referred to rufrscms as (almost) 

 perbaps a subspecies. The only thing that seems to point to 

 hybridity is its non-fruiting, though Dr. Tisehus bas sent me 

 Swedish specimens, named " P. spathulatus Schrad.," with abun- 

 dance of fruit ; but these Swedish specimens are not exactly the 

 same as the original plant of Schrader, and seem to me to be only a 

 state of ru/escens, produced by the water-level having become higher 

 after the plant had flowered and fruited under normal conditions. 

 In Flora for April 12th, 1849, Dr. Schultz has an excellent article 

 on this plant, and says that wherever it grows it occurs where P. 



ohUmyu* (polytjonifoUitH) and P. rufesan* grow abundantly in com- 

 pany, and that the flowers always remain closed. This is strong 

 evidence of hybridity, but the plant in habit is ruff sir ns. I should 

 much like to obtain a plant to cultivate. 



P. "hybkidus Michx.," ex Makino ! in Illustrations of the Flora 

 of Japan, t. 55, No. 9, p. 2 (1891), is P. cristatus Begel et Maack; 

 Flora Ussuriensis, t. 10, figs. 3-6, p. 9 (1861). 



P. nippomcus Makino, 111. Flora of Japan, t. 56, No. 9, p. 2 

 (1891), seems to be referable to P. alpinus Balbis (rufescens Schrad.). 

 Specimens gathered by the Abbe Faurie (Herb. Mus. Paris) in 

 Japan seem to be the plant of Makino ; but unfortunately they are 

 in very bad condition, and not sufficient to decide upon. 



P. Miduhikimo Makino ! 111. Fl. Japan, t. 54, No. 9, p. 2 (1891), 

 is evidently a new species, combining the habit and foliage of J '. 

 hijbridus Michx. with the fruit of pusillus L. It was distributed 

 from Japan by the late M. Maximowicz as " P. hybridus Michx.," 

 mixed with P. jaraaicus Hasskl. 



P. tricarinatus F. Muell. & Ar. Benn., sp. n. — Stem simple (?), 

 5-20 in. long. Submerged leaves almost all decayed before 

 flowering (or before mature fruit is formed), apparently lanceolate, 

 semi-translucent, and papery in texture, with few nerves. Upper 

 (floating) leaves coriaceous, elliptical, 15-21 lines long, 9-12 lines 

 broad; 15-17-nerved, with very numerous anastomosing cross- 

 veins ; under side of lamina with strongly-netted areolation, more 

 prominent towards the midrib; petioles 10-15 lines long, chan- 

 nelled. Stipules soon decaying, 10-15 lines long, acute, semi- 

 translucent, but the veins not prominent. Peduncles nearly equal, 

 moderately stout, 16-22 lines long. Spikes 2-8, dense-flowered, 

 obtuse, 11-18 lines long. Sepals (perianth-leaves) orbicular. 

 Fruit (drupelets) 1| line long, f line broad, compressed, pale 

 yellowish green (or "bright green), the ventral face very slightly 

 curved, the dorsal semicircular for two-thirds, then depressed to 

 the beak, the central keel and lateral ridges (keels) carinated and 

 tuberculakd, central keel extending to the degression ; 2-1 strong 

 tubercles just below the base of the keel, on the side of the 



