eclipta
Eclipta prostrata                                         

Identifying Characteristics:

Seed:  brown, widest at apex and tapering to base, inconspicuous tuft of very short trichomes

Seedling:  Hypocotyle light green to light purple to pink; cotyledons small, green, spatulate, midvein evident on lower surface

Mature Plant: fibrous roots from shallow taproot; erect stem, spreading or prostrate; freely branched, rooting at nodes, green becoming reddish brown or purplish; opposite leaves, simple, petiole lacking, slightly thickened, midvein evident, 2 solitary inflorescence heads, terminal head matures before elongated axillary head, perfect, white

Method of Propagation: seed

Life Cycle: annual herb

References: 
Bryson, Charles T. & Michael S DeFelice. "Weeds of the South."