( ( These cells ) ( ( form ( two ( of ( the ( four ( embryonic membranes ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT These) (NNS cells)) (VP (VBP form) (NP (NP (CD two)) (PP (IN of) (NP (DT the) (CD four) (JJ embryonic) (NNS membranes))))) (. .)))
These cells form two of the four embryonic membranes.
(ROOT (S (NP (CD Two) (NNS membranes)) (VP (VBP form) (NP (NP (DT the) (NN mitochondrion) (NN structure)) (PP (IN of) (NP (DT a) (NN cell))))) (. .)))