( both ( ( ( tend ( to ( be ( ( ( washed out ) ( of ( the atmosphere ) ) ) ( before ( they ( ( ( reach ( the stratosphere ) ) , ) ( for ( the ( most part ) ) ) ) ) ) ) ) ) ) . ) -RRB- ) )
(ROOT (S (NP (DT both)) (VP (VBP tend) (S (VP (TO to) (VP (VB be) (VP (VBN washed) (PRT (RP out)) (PP (IN of) (NP (DT the) (NN atmosphere))) (SBAR (IN before) (S (NP (PRP they)) (VP (VBP reach) (NP (DT the) (NN stratosphere)) (, ,) (PP (IN for) (NP (DT the) (JJS most) (NN part))))))))))) (. .) (-RRB- -RRB-)))
both tend to be washed out of the atmosphere before they reach the stratosphere, for the most part.)
(ROOT (S (NP (DT The) (NN stratosphere)) (VP (VBZ is) (NP (DT the) (NN heat) (NN source))) (. .)))