From the ROOT home page root.cern.ch/root/html524/TTree.html .
I suspect therefore that “Search” is not bothering to look for information in the Reference Manual, which is a shame, because this is one of the best places to look. (I also doubt if it is searching the User Manual or RootTalk digest).
If I am correct, could you please modify this “Search” tool to search these additional sources of information ?
Even more surprisingly, if I go to the Reference Manual page root.cern.ch/drupal/content/reference-guide and type “TTree” into the search window “Use this field for a quick search of the reference guide:”, it still fails to find the TTree reference guide documentation. So I suspect this search is not working properly either.