I'm fairly certain it's not cucumber...If you have an idea why not share?
Well...I really didn't want to spoil the opinions of neutral observers with my erroneous ID.
So far, I think it may be a "Grape ivy", Cissus rhombifolia, which is a three leaved ivy generally put into interior plantings due to it's lack of hardiness. No, we are not talking about grapevine, here, either. The plant I am attempting to ID was taken from a heavily landscaped urban area with no exposure to poison ivy.
I have had poor luck finding anything definitive on this plant, and some sources have stated that it is the same thing as Baltic ivy. I am familiar with Baltic ivy, and it isn't this plant.
Mostly, what I am finding are non-technical "plant guide" sort of references, that don't really give differential identification information. Most pictures I have found are similar, but invariable show a prominent petiole (the little stem from the leaflet to it's attachment) and glossy leaves, which my plant does not seem to have.
Some links I have found:
Cissus rhombifolia known as grape and oak-leaf ivy.
PlantFiles: Detailed information on Grape Ivy, Oak Leaf Ivy Cissus rhombifolia
Untitled Page (pics show long petioles not present on my plant)
Cissus rhombifolia Pictures (leaves are different)
BTW: this is almost certainly NOT poison ivy, as the plant came to my attention last week from an employee working in the landscape who is highly allergic to PI. So far: no irritations, so I am assuming it isn't PI or poison oak.