( ( ( sexual reproduction ) ( usually ( by motile ) ) ) ( isogametes . ) )
(ROOT (S (NP (NP (JJ sexual) (NN reproduction)) (PP (RB usually) (IN by) (NP (NN motile)))) (VP (VBZ isogametes)) (. .)))
sexual reproduction usually by motile isogametes.
(ROOT (S (NP (JJ Sexual) (NN reproduction)) (ADVP (RB usually)) (VP (VBP occur) (PP (IN during) (NP (NP (NNS times)) (PP (IN of) (NP (JJ environmental) (NN stress)))))) (. .)))