( Snakes ( ( ( smell ( with ( ( ( their tongues ) and ) ( an organ ) ) ) ) ( in ( ( the roof ) ( of ( their mouth ) ) ) ) ) . ) )
(ROOT (S (NP (NNS Snakes)) (VP (VBP smell) (PP (IN with) (NP (NP (PRP$ their) (NNS tongues)) (CC and) (NP (DT an) (NN organ)))) (PP (IN in) (NP (NP (DT the) (NN roof)) (PP (IN of) (NP (PRP$ their) (NN mouth)))))) (. .)))
Snakes smell with their tongues and an organ in the roof of their mouth.
(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.