The nodes are backup growth eyes. If the upper portion is damaged, then the nodes often sprout a keikei.
The plant is mounted on bark-free balsam fir I found lying around in the woods!
I don't think we have balsam fir here, but I know we do have fit, now I will have something else to look for while hiking this year! Did you have to do anything to the fir to prep it before mounting the orchid since the bark is not on it?