What did Jem do when Mrs. Dubose said Atticus "lawed for niggers?" And what did Jem learn from his encounter with Mrs. Dubose and her following death?

    Neither Jem nor Scout took very kindly to friends, neighbors or relatives who verbally attacked Atticus over his decision to defend Tom Robinson in Harper Lee's novel, To Kill a Mockingbird. Cousin Francis had already felt the wrath of Scout's knuckles, and now it was Jem's turn to vent his anger.
    The children had never enjoyed passing by Mrs. Dubose's house, where she let loose long insults and tirades about many subjects, but they had been taught to be polite, so they rarely responded in an unfriendly manner. But, then one day, the old lady went too far.

    "Not only a Finch waiting on tables but one in the courthouse lawing for niggers!" 
    Jem stiffened. Mrs. Dubose's shot had gone home and she knew it.
    "... Your father's no better than the niggers and trash he works for!"

After stopping by Elmore's Department Store to buy Scout the baton she had longed for, he took it and "ran flailing wildly up the steps into Mrs. Dubose's front yard." From there,

he did not begin to calm down until he had cut the tops off every camellia bush Mrs. Dubose owned...

    Atticus formulated a fitting punishment for Jem, however. Jem would have to read to Mrs. Dubose every afternoon for a month. It was torture at first, but Jem learned to tolerate the old woman, but he never took a liking to her.

    "Thought you could kill my Snow-on-the-Mountain, did you? Well, Jessie says the top's growing back out. Next time, you'll know how to do it right, won't you? You'll pull it up by the roots, won't you?"
    Jem said he certainly would.

Finally, she dismissed him. Some time later, Atticus visited Mrs. Dubose's house one night. When he returned, he announced to Jem that she had died, but that she had kicked her secret morphine addiction that had made her so miserable, so temperamental. And she had left a present for him. It was a perfect camellia--a Snow-on-the-Mountain. She had bested him again, even in death.
    Later, Atticus explained to Jem that despite her slurs against him, "she was a great lady." When Jem angrily questioned his opinion, Atticus explained that it took great courage to kick the addiction, and that Jem's reading took her mind off her pain. Jem learned, as Atticus told him, that "She was the bravest person I ever knew."