( ( ( ( ( Reptiles ( smell ( using ( ( the tip ) ( of ( their tongue ) ) ) ) ) ) , ) and ) ( ( a ( forked tongue ) ) ( ( allows them ) ( to ( sense ( ( from ( which direction ) ) ( ( a smell ) ( is coming ) ) ) ) ) ) ) ) . )
(ROOT (S (S (NP (NNS Reptiles)) (VP (VBP smell) (S (VP (VBG using) (NP (NP (DT the) (NN tip)) (PP (IN of) (NP (PRP$ their) (NN tongue)))))))) (, ,) (CC and) (S (NP (DT a) (JJ forked) (NN tongue)) (VP (VBZ allows) (NP (PRP them)) (PP (TO to) (NP (NP (NN sense)) (SBAR (WHPP (IN from) (WHNP (WDT which) (NN direction))) (S (NP (DT a) (NN smell)) (VP (VBZ is) (VP (VBG coming))))))))) (. .)))
Reptiles smell using the tip of their tongue, and a forked tongue allows them to sense from which direction a smell is coming.
(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.