later class watched stones of <apostrophe><apostrophe> too , on clouds ?
(ROOT_0 (S_0 (ATS_3 (ATS_1 (RB_1 later) (NP_5 (NN_3 class))) (VP_3 (ATVP_3 (ATVP_2 (ATVP_4 (VBD_2 watched) (PP_2 (ATPP_0 (NP_4 (NNS_1 stones)) (IN_1 of)) (APOSTROPHE_0 <apostrophe><apostrophe>))) (ADVP_0 (RB_0 too))) (COMMA_0 ,)) (PP_2 (IN_0 on) (NP_3 (NNS_1 clouds))))) (DOT_0 ?)))