( Prochlorophytes ( ( ( appear ( to ( be ( ( the ( only ( natural oxygen ) ) ) ( producing ( organisms ( that ( ( do not ) ( contain ( pure chlorophyll ) ) ) ) ) ) ) ) ) ) ( ( a , ) ( as ( do ( ( ( ` ( normal ( ' algae ) ) ) and ) ( land plants ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNS Prochlorophytes)) (VP (VBP appear) (S (VP (TO to) (VP (VB be) (NP (NP (DT the) (RB only) (JJ natural) (NN oxygen)) (VP (VBG producing) (NP (NP (NNS organisms)) (SBAR (WHNP (WDT that)) (S (VP (VBP do) (RB not) (VP (VB contain) (NP (JJ pure) (NN chlorophyll)))))))))))) (NP (NP (SYM a)) (, ,) (SBAR (IN as) (S (VP (VBP do) (NP (NP (`` `) (JJ normal) ('' ') (NN algae)) (CC and) (NP (NN land) (NNS plants)))))))) (. .)))
Prochlorophytes appear to be the only natural oxygen producing organisms that do not contain pure chlorophyll a , as do 'normal' algae and land plants.
(ROOT (S (NP (NNS Plants)) (VP (CONJP (RB not) (JJ only)) (VP (VBP contribute) (NP (NN food))) (CC but) (VP (VBD oxygen) (PP (IN for) (NP (NNS organisms))))) (. .)))