( ( During ( the ( haploid stage ) ) ) ( , ( ( the spores ) ( ( ( ( develop ( into gametophytes ) ) ( -LRB- ( or ( ( gamete-producing plants ) -RRB- ) ) ) ) ( that ( ( produce ( ( haploid gametes ) ( -LRB- ( ( ( eggs and ) sperm ) -RRB- ) ) ) ) ( by mitosis ) ) ) ) . ) ) ) )
(ROOT (S (PP (IN During) (NP (DT the) (JJ haploid) (NN stage))) (, ,) (NP (DT the) (NNS spores)) (VP (VBP develop) (PP (IN into) (NP (NNS gametophytes))) (PRN (-LRB- -LRB-) (CC or) (VP (VBG gamete-producing) (NP (NNS plants))) (-RRB- -RRB-)) (SBAR (IN that) (S (VP (VBP produce) (NP (NP (JJ haploid) (NNS gametes)) (PRN (-LRB- -LRB-) (NP (NP (NNS eggs)) (CC and) (NP (NN sperm))) (-RRB- -RRB-))) (PP (IN by) (NP (NNS mitosis))))))) (. .)))
During the haploid       stage, the spores develop into gametophytes (or gamete-producing plants)       that produce haploid gametes (eggs and sperm) by mitosis.
(ROOT (S (NP (DT The) (JJ haploid) (NN gametophyte)) (VP (VBZ produces) (NP (NNS gametes)) (PP (IN through) (NP (NNS mitosis)))) (. .)))