I'm grateful to be part of this, too!

Some plants are parasitic and able to get their energy and carbon from other plants. Mistletoe is a fairly well-known example of a parasitic plant: it grows into other plants, usually trees, and extracts everything it needs to survive from the tree that it is living on. There are many other kinds of parasitic plants as well.

Of course, the host plant does need light, and if it dies, then so does the parasite, but the parasite itself doesn't need light as long as the host remains alive.

Great to hear that you're still interested in learning more about plants. They do some crazy things and grow in areas where we could never survive. Plants that don't require sunlight have two alternative strategies that they employ. 1st are parasitic plants. These guys have evolved to suck nutrients and water from other plants without the necessity for photosynthesis. While some parasitic plants photosynthesize (like mistletoe) there are others the purely sap the life out of other plants. A cool one is Dodder or Witches Hair click here to read). This plant uses a small structure called haustoria to puncture other plants and use their energy to survive.

2nd are saprophytic plants. These plants feed on decomposing organic material in the soil and gain enough energy from this material that they don't need to photosynthesize. The organic matter they utilize is often fungi in the soil. Examples are coral root orchids (http://en.wikipedia.org/wiki/Corallorhiza_maculata). These two strategies could have evolved for any number of reasons. Plants are very good at adapting to different environments and finding energy when they need it.