496 



NATURAL HISTORY OF PLANTS. 



drupaceous, finally nucamentaceous by desiccation of thin exocarp, 

 armed at apex by style, at base by indurated prickles ; endocarp 

 hard, 1 -seeded. Seed subpendulous orthotropous ; integument 

 thin ; embryo exalbuminous straight (green) ; radicle short inferior ; 

 cotyledons 2, thick fleshy; plumule substipitate, with go leaves 

 verticillate, 2 lower opposite alternating with thicker cotyledons. — 

 A submerged, much branching herb ; stem and branches rather 

 rigid terete, nodose-articulate ; leaves verticillate sessile, 2- or 3- 

 chotomously plurisect ; segments transversely septate dentate acute ; 

 flowers solitary axillary [Northern Hemisphere in both Worlds). See 

 p. 479. 



