FLORA OF THE DISTRICT OF COLUMBIA. 155 



6. VACCAMA Medic. 



1. Vaccaria vulgaris Host. Cowhe«b. 



Occasional about Washington and Rosslyn. Adventive from Eur. in many parts 

 of the U. S. (Saponaria vaccaria L.; V. vaccaria Britton.) 



6. SAPONARIA L. 

 1. Saponaria officinalis L. Bouncing bet. 



Common in waste ground and along roadsides. June-Oct. Native of Eur.; widely 

 naturalized in the U. S. 



Theflowers are often double; they vary in color from almost white to deep pink. 



55. NYMPHAEACEAE. Waterlily Family. 



Petals very small and thick, green; sepals much larger than the petals, green, tinged 

 with yellow; fruit naked; leaves usually longer than broad, green. 



\. NYMPH AEA. 



Petals large and showy, white or pinkish; sepals equaling or shorter than the petals, 

 green; fruit covered with the bases of the petals; leaves as broad as long, purple 

 beneath 2. CASTALIA. 



1. NYMPH AEA L. 



1. Nymphaea advena Soland. Yellow pondlily. 



Shallow water or marshes; common. May-Sept. Northern states, south to N. C. 

 (Nuphar advena Ait.) 



A colony of plants is shown in plate 24. 



2. CASTALIA Salisb. 



1. Castalia odorata (Dryand.) Woodv. & Wood. White waterlily. 



Floating in water, Fourmile Run, Laurel, near Alexandria, and probably elsewhere; 

 formerly found in pools at Great Falls. June-July. Eastern N. Amer. {Nymphaea 

 odorata Ait.) 



56. CABOMBACEAE. Water-shield Family. 



Leaves mostly dissected into numerous capillary lobes; stamens 3-6.. 1. CABOMBA. 

 Leaves oval, the petiole attached to the middle of the blade; stamens 12-18. 



2. BRASENIA. 

 1. CABOMBA Aubl. 



1. Cabomba caroliniana A. Gray. 



Well established formerly in the fishponds in Potomac Park, but these have been 

 filled and the plants destroyed; reported by Steele from the Eastern Branch, 

 Southeastern U. S. 



Sometimes known as Washington plant. 



2. BRASENIA Schreb. 

 1. Brasenia schreberi Gmel. Water-shield. 



Edges of pools along the Potomac near Little Falls; Laurel; rare. June-T;]y. 

 Eastern N. Amer. and on the Pacific coast; also Cuba and Mex. (B. peltata Pursli.) 



57. CEEATOPHYLLACEAE. Hornwort Family. 



1. CERATOPHYLLUM L. Hornwout. 



1. Ceratophyllum demersum L. 



Ponds and sluggish streams near the Potomac from Plummers Island southward; 

 frequent. Throughout the U. S. 



Readily propagating by buds; rarely fruiting. 



