peanut v legumes

http://www.wisegeek.org/what-is-the-difference-between-a-nut-and-a-legume.htm




The thing that sets legumes apart from nuts is that they are from one certain family of plants, called either the fabaceae or leguminosae family. They also contain a lot of seeds. It's not uncommon for a pea pod to have half a dozen peas.  Most of legumes are "dehiscent," opening naturally along a seam on two sides. The pea pod is an obvious example of this. They contain seeds that are attached to their pods, rather than simply fitting within them. Legumes are known for having fruit that is high in protein, and they can make nitrogen in soil. That makes legumes good for use in crop rotations.
Looking only at these thing they have in common, it can be difficult to find out whether a peanut is a legume or a nut. It contains two seeds, the pod is indehiscent, and the seed is not attached to the ovary wall. Despite its name, a peanut is a legume and not a nut. This is why some people who have allergies to some nuts can still eat peanuts, and other people with peanut allergies can eat real nuts.