Field pennycress flowers. Coloured SEM (scanning electron micrograph) of the developing flowers of the field pennycress (Thlaspi arvense). The flowers house the male reproductive organ (stamen), which is topped by a pollen sac (lower centre, brown, anther). The flowers also contain the female reproductive organ (carpel, not seen). Pennycress is considered an agricultural weed, that grows on waste ground and field headlands throughout Europe, USA, east Asia & north Africa. It is also known as the stinkweed due to its unpleasant smell. It may be used as a salad leaf, but can be poisonous to livestock. Magnification: x20 at 6x7cm size.