( ( The nucleus ) ( ( is ( enclosed ( by ( ( ( a ( double membrane ) ) , ) ( the ( nuclear envelope ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT The) (NN nucleus)) (VP (VBZ is) (VP (VBN enclosed) (PP (IN by) (NP (NP (DT a) (JJ double) (NN membrane)) (, ,) (NP (DT the) (JJ nuclear) (NN envelope)))))) (. .)))
The nucleus is enclosed by a double membrane, the nuclear envelope.
(ROOT (S (NP (NNP Nuclear) (NNP enevelope)) (VP (VBZ is) (NP (NP (DT a) (JJ double) (NN membrane)) (PP (IN of) (NP (NP (DT the) (NN nucleus)) (SBAR (WHNP (WDT that)) (S (VP (VBZ encloses) (NP (DT the) (JJ genetic) (NN material))))))))) (. .)))