"Old Nanny sat there rocking Janie like an infant and thinking back and back. Mind-pictures brought feelings, and feelings dragged out dramas from the hollows of her heart."
I believe that this quotation is saying that Nanny misses the younger Janie. She misses the way Janie acted when she was a child. Now, Janie is getting married, and has a life of her own. While Nanny is getting old, and becoming a 'cracked plate.' Nanny was rocking Janie to try to bring back some of the old memories before they were forgotten. I think that Janie honestly misses those days too, in a way. She probably just doesn't want to admit it because there is nothing she can do about it now. Little does she know, Nanny feels the same way.
Chapter 2 - Page 16
http://www.sdst.org/shs/library/images/hurston10.bmp