Brassicaceae: Mustard Family — Cress
Members of the mustard family all have four petals, usually in a cross shape (hence Cruciferae; the old name for the family). With some groups, the flowers are quite similar, so it helps to pay close attention to the fruits. This is especially true for the mustards themselves (Brassica, Hirschfeldia, Sisymbrium, Caulanthus and Turritis).
Fruits in the Mustard family are of two kinds, siliques and silicles. Siliques are at least twice as long as they are wide, while silicles are less elongated. Some siliques are more or less cylindric, others (as in the Wild Radish) are noticeably fatter at the base and taper towards the tip. Some silicles are erect and appressed to the stem, others grow outwards and curve upwards, or outwards and curve downwards.