Hard for me to tell from this photo but it looks like a crab spider to me. They are very interesting - can change colors as part of their camouflage technique. I'm sure someone else will be able to offer a more confident ID.

ETA

http://www.everythingabout.net/articles/biology/animals/arthropods/arachnids/spiders/crab_spider/

Thanks, sikibby! I'll try to take another photo when my camera battery is fully charged.

Thanks, NHBabs, I'll try a camera photo tomorrow and post on that forum.

We have those spiders in the basement. I do my best to ignore them completely!

Looks like the very common spiders that we have everywhere. I think they are yellow sac spiders.

Lalala, you may be right.

Update. This spider has moved on to other places; I hadn't seen it on the plant in many days. Though not a spider "fan" I have respect for them. When I worked in a garden center, the head grower yelled at those who wanted to kill this particularly large spider found on a plant. He called that spider his secret, biological weapon and told everyone to leave it alone.