Why did Darry call Ponyboy at the end of chapter 11? Why was this so important to Ponyboy?

Throughout the novel, Darry is trying as hard as he can to keep his family together.  It shouldn't be his responsibility.  It should be his parents' job, but they are dead.  Because of that, the head of household job falls on Darry as the oldest brother.  Darry is hard on his little brothers, and Ponyboy thinks it is especially directed at him.  Pony goes through most of the novel thinking that Darry doesn't love him or appreciate him.  That starts to change after Darry shows up at the hospital worried sick about Ponyboy and Johnny.  By the end of the novel, their relationship is getting better.  It's not great, but it is getting better.  The entire situation is important to Ponyboy, because he is now realizing and seeing that his oldest brother really does love him and care for him.  They might not always get along, but they do all care for each other.