On reflection, the parts will hold together.
( ( On reflection ) ( , ( ( the parts ) ( ( will ( hold together ) ) . ) ) ) )
(ROOT (S (PP (IN On) (NP (NN reflection))) (, ,) (NP (DT the) (NNS parts)) (VP (MD will) (VP (VB hold) (ADVP (RB together)))) (. .)))
The parts look like they could fall apart, but I'm not sure. 
( ( ( ( ( ( The parts ) ( look ( like ( they ( could ( fall apart ) ) ) ) ) ) , ) but ) ( I ( ( 'm not ) sure ) ) ) . )
(ROOT (S (S (NP (DT The) (NNS parts)) (VP (VBP look) (SBAR (IN like) (S (NP (PRP they)) (VP (MD could) (VP (VB fall) (ADVP (RB apart)))))))) (, ,) (CC but) (S (NP (PRP I)) (VP (VBP 'm) (RB not) (ADJP (JJ sure)))) (. .)))