Here is a picture of an Acer japonicum 'Oregon Fern' that I obtained from a friend. It looks a lot like A.j. 'Green Cascade' but to me the leaves have a more "frilly" appearance. Although the leaf resembles 'Green Cascade' it is said to have the growth habit of A.j. 'Aconitifolium'.
Here is an updated photo of my Acer japonicum 'Oregon Fern'. For awhile I thought that I was going to lose it as it showed some dieback and stem necrosis but with a little care and a transplanting it has rallied and is doing better. This photo was made 4-14-04.
The Oregon Fern grows as a semi-cascading tree. The growth habit is similar to Green Cascade. The leaves are finer than green cascade. The tree itself seems to growth slightly faster than Green Cascade.
During spring and summer this cultivar looks like the basic japonicum, but in the fall, it's incredible. Last October my Oregon Fern displayed deep purple, purple/red, red, orange, yellow and green, sometimes all on the same leaf. It was a kaleidoscope and considerably brightened a drab space in my garden. This photo was taken May 16, 2007.
Duplicate Thread but here's a sloppy photo I took at The US National Arboretum during late May of 2006. This cultivar is much wider than it is tall.