1922] 



PFEIFFER — MONOGRAPH OF THE ISOETACEAE 187 



anastomosing crests; commissural ridges irregular; microspores 

 yellow-brown, 31-45 \i long, smooth. 



Distribution : British Isles, north and central Europe. 



Specimens examined: 



British Isles: 

 Scotland: Loch Brandy, Clova, Croall llj.18 (Mo. Bot. Gard. 



Herb, and N. Y. Bot. Gard. Herb.) ; Loch Callater, Aber- 

 deenshire, July, 1856, Croall (U. S. Nat. Herb.); Loch 

 Cluny, Perthshire, September, 1850, Walker-Arnott (N. Y. 

 Bot. Gard. Herb.); "Scotland," Ward (N. Y. Bot. Gard. 

 Herb.) ; Loch Brandy, Forfarshire, August, 1837, Brand 

 oc. Bot. Edin. 183) (N. Y. Bot. Gard. Herb.); Loch 

 Brandy, Clova, August, 1837, Balfour (N. Y. Bot. Gard. 

 Herb.) ; in a little lake near the Trossach's toward Callan- 

 der, July, 1871, without collector (Gray Herb.) ; Loch Lo- 

 mond, without date or collector (Gray Herb.). 



Wales: Llanberis, 10 June, 1870, Butter (Mo. Bot. Gard. Herb.) ; 



Lake Llyn Padark, 20 August, 1862, Gay (Gray Herb.); 

 Crom y glo, North Wales, 12 November, 1862, Gay (?) (Mo. 

 Bot. Gard. Herb, and Gray Herb.) ; Phrynon Vrech, 23 

 August, 1862, without collector (Mo. Bot. Gard. Herb.). 



France: Lac de Gerardmer, Vosges, 16 July, 1858, Cosson (Mo. 



Bot. Gard. Herb.) ; Lac de Guery, Puy-de-D6me, 23-24 Aug- 

 ust, 1861, Durieu (Mo. Bot. Gard. Herb.) ; Lac de Guery, 

 24 August, 1861, Gay (Gray Herb.) ; Lac de Guery, Puy-de- 

 Dome, August, 1890, Hy (Mo. Bot. Gard. Herb.) ; Lac de 

 Gerardmer, 15 October, 1856, Jacquel (Mo. Bot. Gard. 

 Herb.) ; Lac de Guery au Mont Dore, 16 August, 1877, Al- 

 tar d (U. S. Nat. Herb.) ; Lac de Gerardmer, near St. Die, at 

 bottom of water on granitic soil, 25 September, 1851, Billot 

 (U. S. Nat. Herb.) ; in Lake Gerardmer, August, 1864, Perrin 

 Gray Herb, and N. Y. Bot. Gard. Herb.) ; mountain lake, 

 Chauvet, in Arvernia, 27 August, 1861, Gay (Gray Herb.) ; 

 Lac de Bruyeres, dans les Vosges, Hornung (N. Y. Bot. 

 Gard. Herb.) ; Longemer, 2 July, 1881, Study (N. Y. Bot. 

 Gard. Herb.); in bottom of Lakes Gerardmer, Longemer, 

 and Retournemer, all the year (Stirp. Crypt. Vog.-Rhen., 

 1810-26), Mougeot & Nestler 111 (N. Y. Bot. Gard. Herb.) ; 

 lakes of the Vosges, 1833, Mougeot (N. Y. Bot. Gard. 

 Herb.) ; in deep pools and ponds, through almost all the 



