66 CLASS V. ORDER I. 



This has no floating leaves, the flowers only appearing above 

 water. — July. 

 PoTAMOoETON LucENs. Mx, Shining Pond weed. 



Leaves lanceolate, siibsessile with a thick midrib; 

 spikes long, cylindrical. 



A very long, large leaved species. Leaves immersed. — 

 Ditches, &c. — July. 



PoTAMOGETON sETACEUM. WHM. Sctttceous Pond wccd. 

 Upper leaves opposite, lanceolate, five nerved, on 

 short petioles ; lower ones alternate, filiform; spikes 

 dense, sliorter than the leaves. 



Very different in size from any of the preceding, the whole 

 plant being small and slender. — July. 



PoTAMOGETON PAuciFLORUM. Short headed Pond weed. 



Leaves sessile, linear, flat ; heads about four flow- 

 ered. 



This species is not spiked, the flowers forming a little terilu- 

 nal head or whorl, a few together. — July. 



75. RUPPIA. 



RuppiA MARiTiMA. L. Sea Ruppia. 



An immersed, grass like plant, of salt water ditches and ponds. 

 Leaves linear, all under the surface. Spike or head above 

 water, about four flowered. Seeds four or five on pedicels. — 

 South Boston, &c. — July. 



Class V. PENTANDRIA. Five stamens. 



Order I. MONOGYNIA. One style. 



A. Floivers monopetalous, inferior, with four naked seeds. 



76. EcHiuM. Corolla irregular, bell shaped, with 

 the throat naked : stigma two cleft. 



77. LiTHosPERMUM. Corolla infundibuliform with 

 the throat naked; calyx five parted. 



