( Snakes ( ( ( smell ( scents ( in ( ( the air ) ( using ( their ( forked tongue ) ) ) ) ) ) ) ( -LRB- ( ( see ( Figure 19.22 ) ) -RRB- ) ) ) . ) )
(ROOT (S (NP (NNS Snakes)) (VP (VBP smell) (NP (NP (NNS scents)) (PP (IN in) (NP (NP (DT the) (NN air)) (VP (VBG using) (NP (PRP$ their) (JJ forked) (NN tongue)))))) (PRN (-LRB- -LRB-) (S (VP (VB see) (NP (NNP Figure) (CD 19.22)))) (-RRB- -RRB-))) (. .)))
Snakes smell scents in the air using their forked  tongue (see Figure 19.22).
(ROOT (S (NP (NNS Snakes)) (VP (VBP use) (NP (PRP$ their) (NN tongue)) (PP (TO to) (NP (NN smell) (NNS things)))) (. .)))
Snakes use their tongue to smell things.