( ( Features ( of ( ( pollen grains ) ( used ( in identification ) ) ) ) ) ( ( are ( ( ( ( ( ( size , ) shape ) , ) ( thickness ( of ( ( the exine ) ( -LRB- ( ( outer wall ) -RRB- ) ) ) ) ) ) and ) ( ( intine ( -LRB- ( ( inner wall ) -RRB- ) ) ) ( of ( the ( pollen grain ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (NNS Features)) (PP (IN of) (NP (NP (NN pollen) (NNS grains)) (VP (VBN used) (PP (IN in) (NP (NN identification))))))) (VP (VBP are) (NP (NP (NP (NN size)) (, ,) (NP (NN shape))) (, ,) (NP (NP (NN thickness)) (PP (IN of) (NP (NP (DT the) (NN exine)) (PRN (-LRB- -LRB-) (NP (JJ outer) (NN wall)) (-RRB- -RRB-))))) (CC and) (NP (NP (NP (NN intine)) (PRN (-LRB- -LRB-) (NP (JJ inner) (NN wall)) (-RRB- -RRB-))) (PP (IN of) (NP (DT the) (NN pollen) (NN grain)))))) (. .)))
Features of pollen grains used in identification are size, shape, thickness of the exine (outer wall) and intine (inner wall) of the pollen grain.
(ROOT (S (NP (DT Each) (NN pollen) (NN grain)) (VP (VBZ has) (NP (NP (CD two) (NNS coverings)) (: :) (NP (NP (NP (DT the) (NN exine)) (PRN (-LRB- -LRB-) (NP (NP (JJR thicker)) (, ,) (NP (JJ outer) (NN layer))) (-RRB- -RRB-))) (CC and) (NP (DT the) (NN intine))))) (. .)))