natadacetf:. 47 



tween the forks of the stem, scarcely exceeding the spike, slender, 

 not thickened upwards. Sepals with their lamina roundish-rhombic. 

 Fruiting-spike subglobose, dense, few-flowered. Fruit moderately- 

 large, greenish-olive, considerably compressed, not acuminated, very 

 slightly convex on the upper margin, on which there is a large pro- 

 minent tooth near the base, half-obovate and bluntly 3-keeled on the 

 back, terminated by a rather long slightly recurved beak forming a 

 continuation of the upper margin. Plant bright green, retaining its 

 colour when dry. 



In ditches and ponds. Rare. Warehara, Dorset (Mr. I. C. i\Iau- 

 sel) ; Amberly, Sussex (Mr. Borrer); Black Sea, Wandsworth Com- 

 mon (Mr. W. F. Saunders), and Weybridge, Surrey (Mr. H. C. 

 Watson); Higham by Norwich, Haddiscome, Brundall and Buckcn- 

 ham Ferry, Norfolk (Rev. Kirby Trimmer). Probably in some ot the 

 intermediate counties, but liable to be passed over as P. zosterifolius 

 or P. obtusifolius. 



England. Perennial. Summer. 



Stem and foliage very similar to that of P. zosterifolius, but usually 

 a more slender plant, Avith shorter and narrower leaves, 2 to 4 inches 

 long by I to I inch broad, more gradually acuminated, and with 

 stronger stipules. The stem too is usually more branched, and with a 

 greater tendency in the branches to become dichotomous. Still when 

 the plant is not in flower or fruit, it may easily be passed over as a 

 small state of P. zosterifolius. The peduncles, however, are not more 

 than 1 to ij inch long, the spike much shorter, rarely above ^ or f 

 inch long, with very few flowers. The fruit is smaller, \ inch long, 

 flatter, with a strong tooth on the upper margin, and is much more 

 convex on the back, so that the curve is more than a semicircle ; the 

 beak forms a continuation of the upper margin, and is more than twice 

 as long as that of P. zosterifolius. With these differences in the fruit 

 it is impossible to consider it a subspecies of that plant. 



Sharp-leaved Pondweed. 



French, Potamot afeuilles acuminees. German, Spitzhldttriges Samkraut. 



SPECIES XVIII.— POT AMOGETON OBTUSIFOLIUS. Mert.&Eoch. 



Plate MCCCCXVII. 



Reich. Ic. Fl. Germ, et Helv. Vol. VII. Tab. XXV. Fig. 43. 

 Billot, Fl. Gall, et Germ. Exsicc. No. 652. 



P. gramineus Sm. Engl. Bot. No. 2253, and Eugl. Fl. Vol. I. p. 235. EooJc. & Am. 

 Brit. Fl. ed. viii. p. 480 (non Linn. Herb.). 



Stem 4-sided, slightly compressed, slender, not foliaceous, repeatedly 

 dichotomous. Leaves all similar, sessile, linear, narrowed towards the 



