( ( Erythroid cells ) ( ( are ( red ( blood cells ) ) ) . ) )
(ROOT (S (NP (JJ Erythroid) (NNS cells)) (VP (VBP are) (NP (JJ red) (NN blood) (NNS cells))) (. .)))
Erythroid cells are red blood cells.
(ROOT (S (NP (NNP Red) (NN blood) (NNS cells)) (VP (VBP are) (NP (DT the) (RBS most) (JJ numerous) (NN blood) (NNS cells))) (. .)))