For the save() operation to be cascaded, you need to enable CascadeType.SAVE_UPDATE, using the proprietary Hibernate Cascade annotation, since save() is not a standard JPA operation. Or you need to use the persist() method, and not the save() method.
E. Ponvert, J. Baldridge, and K. Erk. Proceedings of the 49th Annual Meeting of the Association for Computational Linguistics: Human Language Technologies - Volume 1, page 1077--1086. Stroudsburg, PA, USA, Association for Computational Linguistics, (2011)