CLASS IT. ORDIR I.] DIPSACCS. 173 



1. P. tetraphyl'lum, Linn. (Fig. 214.) four-leaved All-seed. Leaves 



of the stem whorled in fours, those of the branches opposite. 

 English Botany, t. 1031. English Flora, vol. i. p. 188. Lindley, 

 Synopsis, p. 61. Hooker, British Flora, vol. i. p. 59. 



Root long and tapering. Stems numerous, spreading upon the sur- 

 face of the ground, repeatedly branched, and somewhat downy. Leaves 

 obovate, on short footstalks, entire, smooth, and rather succulent, ar- 

 ranged in whorls of four on the stems, and two on the branches, having 

 at the base thin membranous stipula, pointed, with a jagged margin. 

 Floivers terminal, in corymbose branches, each division of which having 

 at its base a pair of acute, membranous, pointed, and jagged bractea. 

 Calyx of five ovate, keeled, pointed pieces, with pale membranous 

 margins, slightly united at the base. Petals five, obovate, notched at 

 the extremity, white, smaller than the calyx leaves, and alternating 

 with them. Stamens from three to five. Styles short. Capsule ovate, 

 of one cell, opening with three valves. Seeds small, numerous, attached 

 to a central placenta. 



Habitat. Southern coasts of England Devonshire, Dorsetshire, 

 and Portland Island. 



Annual ; flowering during the summer months. 



CLASS IV. 



TETRANDRIA. 4 STAMENS (equal) 



ORDER I. 



MONOGYN'IA. 1 PISTIL. 



GENUS I. DIPSA'CUS. LINN. Teatel. 

 Nat. Ord. DIPSA'OEJT. 



GEN. CHAR. Flowers in heads, surrounded by a many-leaved involu- 

 crum. Involucellum with four sides, and eight little excavations. 

 Calyx cup-shaped, thickly clothed with short rigid hairs. Recep- 

 tacle with spiny, glumaceous bractea;, shorter than the leaves of 

 the involucrum. Name from ^*<u, to be thirsty; the upper 

 united leaves holding water in their hollows, by which the thirsty- 

 traveller may be relieved, 



