116 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



Petals unequal, blue or white; filaments naked; perfect stamens 3; bracts heart-shaped, 

 folded, forming a spathe with the margins often partly united; leaves short, ovate 

 to lanceolate 2. COMMELINA. 



1. TRADESCANTIA L. Spiderwort. 



The commoner green-leafed Wandering Jew in cultivation is T. fluviinensis Veil., of 

 South America. 



1. Tradescantia virginiana L. 



Rich woodlands along the Potomac above Washington; common. May-Aug. Conn. 

 toS. C. 



The flowers open at night and the petals collapse by midday. A plant in bloom is 

 shown in plate ISA. 



2. COMMELINA L. Day flower. 



Spathe margins free. Capsule 2-celled, 4-seeded; flowers with 2 blue petals and one 

 smaller white one; seeds rugose; glabrous or somewhat hairy annuals; spathes few, 



axillary, peduncled 1. c. communis. 



Spathe margins united at the base. 

 Capsule with 3 cells, each 1-seeded, or one cell reduced; leaf sheaths and spathes 

 glabrous or with white hairs; plant low, perennial, with a cluster of somewhat 

 fleshy roots; spathes single or few together, peduncled; petals 2, blue. 



2. C. erecta. 



Capsule with 2 2-seeded cells, the other cell with a single larger seed; leaf sheaths 



ciliate with stout brown hairs; plant 60-150 cm. high, perennial by horizontal 



rootstocks; spathes terminal, clustered, sessile; petals 3, blue.. 3. C. virginica. 



1. Commelina communis L. Wild Wandering Jew. 

 A common and persistent weed in gardens and moist soil. July-Oct. N. Y. to Ga.; 



introduced from eastern Asia. 



The stems retain vitality for days after being cut and root readily. The flowers 

 are notable for the contrast of the blue petals and yellow stamens. 



2. Commelina erecta L. 



Along rocky streams, often in dry situations; not common; High Island; Fourmile 

 Run: Great Falls. June-Sept. N. Y. to Tex. (C. virginica of Ward's Flora.) 



3. Commelina virginica L. 



Frequent along margins of the Eastern Branch and Potomac. Aug.-Oct. Eastern 

 U. S. (C. erecta of Ward's Flora; C. hirtella Vahl.) 



23. PONTEDERIACEAE. Pickerel-weed Family. 



Plants erect, 30-120 cm. tall; leaves large, arrow-shaped; flowers in spikes, bright blue. 



1. PONTEDERIA. 



Plants creeping or submerged; leaves linear or reniform; flowers in few-flowered 



spathes, blue, white, or yellow 2. HETERANTHERA. 



1. PONTEDERIA L. 



1. Pon tederia cordata L. Pickerel-weed. 



Abundant in marshes. June-Aug. Eastern U. S. 

 Plate 16 shows a colony in flower in a marsh near Dyke. 



2. HETERANTHERA Ruiz & Pav. 



Leaves reniform; plants creeping on mud; flowers white or pale blue. 



1. H. reniformis. 

 Leaves linear, yrasslike; plants submerged; flowers yellow 2. H. dubia. 



