( Joe ( then ( ( demonstrates ( ( the ( explosive effect ) ) ( of ( ( the gas ) ( produced ( by ( ( lighting ( a match ) ) ( to ( ( the bubbles ) ( adhering ( to ( ( the ( brown scum ) ) ( floating ( on ( top ( of ( the ( water cell ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) . ) ) )
(ROOT (S (NP (NNP Joe)) (ADVP (RB then)) (VP (VBZ demonstrates) (NP (NP (DT the) (JJ explosive) (NN effect)) (PP (IN of) (NP (NP (DT the) (NN gas)) (VP (VBN produced) (PP (IN by) (S (VP (VBG lighting) (NP (DT a) (NN match)) (PP (TO to) (NP (NP (DT the) (NNS bubbles)) (VP (VBG adhering) (PP (TO to) (NP (NP (DT the) (JJ brown) (NN scum)) (VP (VBG floating) (PP (IN on) (NP (NP (NN top)) (PP (IN of) (NP (DT the) (NN water) (NN cell))))))))))))))))))) (. .)))
Joe then demonstrates the explosive effect of the gas produced by lighting a match to the bubbles adhering to the brown scum floating on top of the water cell.
(ROOT (S (NP (NNP Gas) (NN bubble) (NNS holes)) (VP (VBZ helps) (NP (NP (JJ pumice) (NN float)) (PP (IN in) (NP (NN water))))) (. .)))