( ( Two sperm ) ( ( then ( ( ( travel down ) ( the ( pollen tube ) ) ) ( to ( the ( megasporangium ( to ( fertilize ( ( ( ( ( the egg ) ( which ( creates ( a zygote ) ) ) ) , ) and ) ( ( the ( central cell ) ) ( which ( forms ( the endosperm ) ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (CD Two) (NN sperm)) (VP (ADVP (RB then)) (VBP travel) (PRT (RP down)) (NP (DT the) (NN pollen) (NN tube)) (PP (TO to) (NP (DT the) (NN megasporangium) (S (VP (TO to) (VP (VB fertilize) (NP (NP (NP (DT the) (NN egg)) (SBAR (WHNP (WDT which)) (S (VP (VBZ creates) (NP (DT a) (NN zygote)))))) (, ,) (CC and) (NP (NP (DT the) (JJ central) (NN cell)) (SBAR (WHNP (WDT which)) (S (VP (VBZ forms) (NP (DT the) (NN endosperm))))))))))))) (. .)))
Two      sperm then travel down the pollen tube to the megasporangium to      fertilize the egg which creates a zygote, and the central cell      which forms the endosperm.
(ROOT (S (PP (IN After) (NP (NN fertilization))) (, ,) (NP (DT a) (NN zygote)) (VP (VBZ forms) (PP (IN into) (NP (CD two) (NNS cells)))) (. .)))