( ( Living cells ) ( ( ( can only ) ( arise ( from ( ( ( preexisting cells ) , ) ( which ( then ( divide ( to ( produce ( new cells ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (VBG Living) (NNS cells)) (VP (MD can) (ADVP (RB only)) (VP (VB arise) (PP (IN from) (NP (NP (VBG preexisting) (NNS cells)) (, ,) (SBAR (WHNP (WDT which)) (S (ADVP (RB then)) (VP (VBP divide) (S (VP (TO to) (VP (VB produce) (NP (JJ new) (NNS cells)))))))))))) (. .)))
Living cells can only arise from preexisting cells, which then divide to produce new cells.
(ROOT (S (NP (NNS Cells)) (VP (VBP come) (PP (IN from) (NP (VBG preexisting) (NNS cells)))) (. .)))