( Development ( of ( ( an ( embryo sac ) ) ( within ( the sporangium ) ) ) ) )
(ROOT (NP (NP (NNP Development)) (PP (IN of) (NP (NP (DT an) (NN embryo) (NN sac)) (PP (IN within) (NP (DT the) (NN sporangium)))))))
Development of an embryo sac within the sporangium
(ROOT (S (NP (NP (DT The) (JJ amniotic) (NN sac)) (, ,) (SBAR (WHNP (WDT which)) (S (VP (VBD was) (VP (VBG sitting) (PP (IN on) (NP (NP (NN top)) (PP (IN of) (NP (DT the) (JJ flat) (NN embryo))))))))) (, ,)) (VP (VBZ envelops) (NP (DT the) (NN embryo)) (SBAR (IN as) (S (NP (PRP it)) (VP (VBZ folds))))) (. .)))