The present study was conducted to investigate the morphology, anatomy, karyotype, palynology, biogeography and seed germination of Capsella bursa – pastoris. Also, the ecological characteristics and metabolic products were examined. C. bursa – pastoris (shepherd's purse) is annual cruciferous herb shows considerably variety of habit form. It is a serious weed responsible for yield loss of many crops. The stem shows the typical dicot characters, with intervascular cambium gives few secondary tissues and has wide parenchymatous pith. The leaf has adaxial epidermal cells of midrib are large and projecting from the blade. The root shows normal secondary thickening and the ruptured epidermis covered by multilayered periderm. The chromosomes are 2n = 16. Pollen grains are spheroidal isopolar, tricolpate with sinuaperturate. The highest rate of seeds germination attained at 30 - 35º C, low salinity (0 – 0.2 M NaCl) and 25 – 30 mm rainfall. Capsella community comprised 25 species belonging to 15 families. Cynodon dactylon, Urtica urens, Rumex dentatus and Lamium amplexicaule were the common associates. The major life – forms were therophytes, hemicryptophytes and geophytes. The assemblage of this community belongs to six chorotypes with predominance of Mediterranean and Irano – Turanian. Capsella flourished in wet, loose, non – saline soil. The nutritive value was 69.29 cal./ 100g. The residues of the different extracts of leaves, stems and roots were 15.64, 11. 97 and 8.30 %, respectively. The polyphenols and flavonoids were detected in ethyl alcohol, chloroform and acetone extracts. These extracts exhihited antioxidant and antimicrobial spectrum only against. Bacillus cereus, Staphyloccus aureus, Klebsiella pneumoniae, Pseudomonas aeruginosa.