ISOETACE.E. 5 



membranous margins and smooth backs, erect or ascending, straight 

 or recurved, without marginal bast-fibres, and without stomata or with 

 very few. Phyllodes absent. Velum incomplete. Sporangia oblong- 

 ovoid or subglobose, unspotted. Microspores with a white crustaceous 

 integument, tuberculate with prominent blunt or truncated tubercles, 

 which are not higher than broad. 



Var. a. genuina. 



Plate 1826. 



Leaves rarely exceeding 6 or 7 inches in length, stout, more or less 

 recurved when the plants are not crowded ; the membranous margins 

 usually rather narrower than the firm portion of the leaf-base. 



Var. ft. Morel 

 Plate 1826*. 

 I. Morei, D. Moore in Journal of Botany (1878), p. 353. 



Leaves 1 to 2 feet long or more ; more slender and more tapering 

 than in var. a, erect, or with the apices floating ; the membranous 

 margins usually as broad as the firm portion of the leaf-base. 

 Macrospores in more saccate cavities, and fewer in number, and 

 microspores smaller than in var. a. 



Var. a occurs in lakes, growing submerged in the water, almost 

 confined to hilly districts. In Wales it is frequent in Carnarvonshire, 

 and occurs also in Merioneth and Denbigh. Frequent in the Lake 

 district. In Scotland it occurs in most of the counties from the Forth 

 and Clyde north to Caithness and Sutherland. Dr. A. R. Duguid 

 found it in Loch of Carness, Orkney. In Ireland it occurs from 

 north to south, chiefly in mountainous districts, and most plentiful in 

 the west and north. 



Var. /3 is found wholly submerged, or with the leaves floating on 

 the water, in the Upper Lough of Bray, Co. Wicklow. 



England, Scotland, Ireland. Perennial. Summer, Autumn. 



Corm from the size of a cherry-stone to that of a hazel-nut, dark 

 brown exteriorly, white when cut through. Root-fibres developed 

 from the furrow which traverses the bottom of the corm, simple or 

 once or twice forked towards the apex, brown. Leaves 2 inches to 

 1 foot long, deep green, rather rigid, tapering, usually recurved and 

 diverging or erect; their bases dilated, with membranous pale yellow 

 edges, withering and ultimately rotting off from the corm without 



