Narrow-leaf Vetch

This is an annual herb, a distant member of the vine and pea family, with hollow, four-sided, hairless to hairy stems which can reach two meters in maximum length. The leaves are each made up of a few pairs of linear, lance-shaped, oblong, or wedge-shaped, needle-tipped leaflets up to 3.5 centimeters long. The pealike flowers occur in the leaf axils, solitary or in clusters of up to three. The flower corolla is 1 to 3 centimeters in length and whitish to bluish to red or bright pink-purple in color. The fruit is a legume pod up to 6 or 7 centimeters long which is hairy when new and smooth later. It contains up to 12 seeds.

As I was cropping the image, I realized I had accidentally gotten a fantastic demonstration of this plant's extrafloral (or extranuptial)nectaries - these are nectar-secreting plant glands that develop outside the flowers and are not involved in pollination. See the 3rd & 4th image - #3 shows the nectary very clearly while #4 shows an ant or two busy at it. (These glands - which are actually quite common on plants) is thought to serve a defensive function by attracting ants and wasps which in turn protect the plant from other insects as well as foraging herbivores.)