TETRADYNAMIA— SILICULOSA. Draba. 157 



1, S. aquatica. Water Awl-wort. 



S.aquatica. Linn.Sp. Pl.896. Willd. v. 3. 423. Fl.Br.676. Engl. 

 Bot.v.\l.t.732. Hook.Scot.\96. Lond.t.\3o. Dicks. H. Sice, 

 fasc. 5.9. Fl. Dan. t. 35. 



S. erectajunci foliis acutis mollibus. Raii Syn.307. 



Graminifolia aquatica, thlaspeos capitulis rotundis, septo medio si- 

 liculam dirimente. Pink. Almag. 180. Phyt. t.\88.f. 5. 



Gramen junceum hibernicum minus, thlaspios capitulis Sherardi. 

 Moris. V. 3. 229. sect. 8. t.lO.f. 29. 



Irish Rush Cress. Petiv. H. Brit. t. 48./. 8. 



On the sandy or gravelly bottoms of alpine lakes, under water. 



In Lough Neagh, Ireland. Sherard. Lough Carran, Scotland. 

 Dr. Hope. In several other Scottish lakes. Hooker. Also in 

 many of the Welsh lakes. Huds. Mr. Griffith, and Rev. W. 

 Bingley. 



Annual. July. 



Root of numerous, long, white, simple fibres. Stem none. Herb 

 quite smooth. Leaves several, awl-shaped, spreading, an inch 

 or two in length. Fl. few, white, minute, in a simple, stalked, 

 radical, zigzag cluster. Pouches erect. Their partition is er- 

 roneously described in Fl.Br.and. Engl.Bot. as "contrary to 

 the valves "; whereas it is contrary to the greatest diameter of 

 the seed-vessel. 



Dr. Hooker confirms our account of the flowers being always se- 

 veral feet under water, where he observed them to be constantly 

 expanded, so that the impregnation actually takes place in that 

 element. The poZtoi has not been examined. By the excellent 

 plate of this author, so great in botanical dissections, it appears 

 that the radicle is not closely applied to the cotyledons., but they 

 together form a curve, whose two extremities are distant from 

 each other. This I presume is expressed by cotyledones bicrures 

 in Mr. Brown's generic definition. 



318. DRABA. Whitlow-grass. 



Linn. Gew. 333. Jim. 240. Fl.Br.677. Br. in Jit. H. Kew. v. 4.91. 



DeCand. Syst.v. 2. 331. Lam.t.556.f.\,2. Gcertn. t.\4l. 

 Erophila. DeCand. Syst. v. 2. 356. 



Cal. equal at the base, somewhat spreading, deciduous ; 

 leaves ovate, concave. Pet. either cloven, notched or en- 

 tire, spreading, with short claws. Filam. simple. Atii/i. 

 of 2 roundish lobes. Genn. ovate. Stj/le very short, or 

 none. Stigma capitate, flat. Pouch oblong-oval, laterally 

 compressed, entire, tipped with the style or stigma, of 

 2 cells; valves nearly flat, separating from the bottom ; 

 partition membranous, of the same shape and breadth. 



