Finger Lime, Australian Lime: I don’t see this fruit in Markets, but it is acquiring notoriety as “plant caviar.” Breaking open a fruit, you can slurp down the beautifully spherical, emerald cells (juice sacs) that fill around the seed. They pack a citrus punch, as strong as Kumquats.
Botanists call them Citrus australasica, which pretty much tells us their closest relatives are the other citrus.
Because each fruit represents a single carpel, I am guessing Carpologists would lean toward calling this a Camara (a single, indehiscent carpel), but it is so much like a single-section Lime, I think we should honor it as a Hesperidium (see Oranges, etc.).