If one person gives another person an etrog, and that the recipient should pass it along to another person after his own death, then there's a dispute between Rabbi Yehudah HaNasi and Rabban Shimon ben Gamliel as to the degree of ownership by that first recipient. He has to pass it on, so he can't use it in all ways, like an outright owner. Can he sell it, for example? Also, a story about a woman who owned a date palm that was planted in the property of Rav Bibi bar Abaye - and he was regularly upset when she came to harvest the fruit. The Gemara works to figure out what was really upsetting him.