( ( ( The spines ) ( of ( the cactus ) ) ) ( ( are ( its leaves ) ) . ) )
(ROOT (S (NP (NP (DT The) (NNS spines)) (PP (IN of) (NP (DT the) (NN cactus)))) (VP (VBP are) (NP (PRP$ its) (NNS leaves))) (. .)))
The spines of the cactus are its leaves.
(ROOT (S (NP (NP (DT The) (NNS spines)) (PP (IN of) (NP (DT a) (NN cactus)))) (VP (VBP help) (SBAR (S (NP (PRP it)) (VP (VBP survive) (SBAR (IN because) (S (NP (NNS spines)) (VP (VB protect) (NP (DT the) (NN cactus)) (PP (IN from) (NP (NNS animals)))))))))) (. .)))