( ( This ( haploid stage ) ) ( ( is ( ( ( the ( gametophyte stage ) ) , ) ( which ( ( produces gametes ) ( by mitosis ) ) ) ) ) . ) )
(ROOT (S (NP (DT This) (JJ haploid) (NN stage)) (VP (VBZ is) (NP (NP (DT the) (JJ gametophyte) (NN stage)) (, ,) (SBAR (WHNP (WDT which)) (S (VP (VBZ produces) (NP (NNS gametes)) (PP (IN by) (NP (NNS mitosis)))))))) (. .)))
This haploid stage is the gametophyte stage, which produces gametes by mitosis .
(ROOT (S (NP (DT The) (JJ haploid) (NN gametophyte)) (VP (VBZ produces) (NP (NNS gametes)) (PP (IN through) (NP (NNS mitosis)))) (. .)))