( ( Their ( rough faces ) ) ( often ( ( make ( ( excellent surfaces ) ( for ( grinding ( plant seeds ) ) ) ) ) . ) ) )
(ROOT (S (NP (PRP$ Their) (JJ rough) (NNS faces)) (ADVP (RB often)) (VP (VBP make) (NP (NP (JJ excellent) (NNS surfaces)) (PP (IN for) (NP (VBG grinding) (NN plant) (NNS seeds))))) (. .)))
Their rough faces often make excellent surfaces for grinding plant seeds.
(ROOT (S (NP (NN Ground) (NN tissue)) (VP (VBZ makes) (PRT (RP up)) (NP (NP (JJS most)) (PP (IN of) (NP (NP (DT the) (NN inside)) (PP (IN of) (NP (DT a) (NN plant))))))) (. .)))