a series of perfect black pearls clicking together to form a string 
(ROOT (NP (NP (NP (DT a) (NN series)) (PP (IN of) (NP (JJ perfect) (JJ black) (NNS pearls)))) (VP (VBG clicking) (ADVP (RB together)) (S (VP (TO to) (VP (VB form) (NP (DT a) (NN string))))))))
(ROOT (NP (NP (NP (DT ) (NN )) (PP (IN ) (NP (JJ ) (JJ ) (NNS )))) (VP (VBG ) (ADVP (RB )) (S (VP (TO ) (VP (VB ) (NP (DT ) (NN ))))))))