ounce: a unit of weight equal to one sixteenth of a pound or 16 drams or 28.349 grams
avoirdupois unit: any of the units of the avoirdupois system of weights
common watercress: perennial Eurasian cress growing chiefly in springs or running water having fleshy pungent leaves used in salads or as a potherb or garnish; introduced in North America and elsewhere