( ( ( The embryo ) ( within ( the seed ) ) ) ( ( begins ( as ( ( ( a ( single cell ) ) , ) ( the zygote ) ) ) ) . ) )
(ROOT (S (NP (NP (DT The) (NN embryo)) (PP (IN within) (NP (DT the) (NN seed)))) (VP (VBZ begins) (PP (IN as) (NP (NP (DT a) (JJ single) (NN cell)) (, ,) (NP (DT the) (NN zygote))))) (. .)))
The embryo within the seed begins as a single cell, the zygote.
(ROOT (S (NP (PRP We)) (ADVP (DT all)) (VP (VP (VBP start) (PP (IN as) (NP (DT a) (JJ single) (NN cell)))) (CC and) (VP (ADVP (RB soon)) (VBP grow) (PRT (RP into)) (NP (DT a) (PRN (-LRB- -LRB-) (NP (NN n)) (-RRB- -RRB-)) (NN embryo)))) (. .)))