Propagation: Hibiscus Syriacus cuttings, 1 by HelloMissMary

HelloMissMary wrote:
I have some 50+ - year - old shrubs in different varieties on a side of the house that can not be seen. This summer, I dug up some of the "spring-ups" near them and transplanted them to an area where they can be enjoyed (4 of 5 survived). About 2 weeks ago, I took some cuttings and put them in glasses of water. The cuttings from the all-white cultivar almost immediately sprouted little nodes (for lack of a better word) all up and down the stem under the water. None of the other varieties did that. Can someone tell me what these things are?