( ( The petals ) ( collectively ( ( are ( called ( the corolla ) ) ) . ) ) )
(ROOT (S (NP (DT The) (NNS petals)) (ADVP (RB collectively)) (VP (VBP are) (VP (VBN called) (NP (DT the) (NN corolla)))) (. .)))
The petals collectively are called the corolla.
(ROOT (S (NP (NP (DT All)) (PP (IN of) (NP (DT the) (NNS petals)))) (ADVP (RB together)) (VP (VBP are) (VP (VBN called) (NP (DT a) (NN corolla)))) (. .)))
All of the petals together are called a corolla.