141 
This Ruppia is characterized by a stouter and thicker 
stem (1 mm. in diameter or more) with a more developed 
anatomy than the European species have. Leaves always 
obtuse with extremely few and minute, one-celled denticles 
in the very apex. Sheaths long and a little enlarged be- 
F 
Fig'. A. B. Ruppia spiralis Dum.. A, Top of leaf, ,4 /i; B, 
Transverse section of leaf, v. subrigida, 80 /i. C. D. R. maritima L. C, 
1 — 4 Tops of leaves, 12 /i; D, Transverse section of leaf 80 /i. E — H, 
Ruppia obtusa Hagstr. E. Transverse section of leaf, vb, vascular 
bundle, end, endodermis, 1, lacuna, ep, epidermis, so / x ; F. 1 — 3 
Tops of leaves 14 /i; G, Transverse section of stem, ep, end, 1, vb, 
as in E, cc, central cylindre, b bark 35 /i; H, Fruit in outline, ds, 
dorsal side, vs, ventral side, st, stigma, p, stipe 4 /i. 
low. Upwards they are furnished with a little more pro- 
minent ears than R. spir. and marit. have; decaying they 
leave an annulus round the stem. Fruit large as a fruit of 
Potamogeton pectinatus, always nearly quite without stipe 
(only 1 /a— 1 mm. long) and without rostrum, only with a 
wart (the resisting stigma). Pollen almost less curved than 
in our European species, 4 times as long as the broadness. 
