( ( ( The barbs ) ( on ( ( ( the ( arrows ( show ( wind direction ) ) ) ) and ) ( ( the head ) ( of ( the arrow ) ) ) ) ) ) ( ( indicates ( cloud cover ) ) . ) )
(ROOT (S (NP (NP (DT The) (NNS barbs)) (PP (IN on) (NP (NP (DT the) (JJ arrows) (NN show) (NN wind) (NN direction)) (CC and) (NP (NP (DT the) (NN head)) (PP (IN of) (NP (DT the) (NN arrow))))))) (VP (VBZ indicates) (NP (NN cloud) (NN cover))) (. .)))
The barbs on the arrows show wind direction and the head of the arrow indicates cloud cover.
(ROOT (S (NP (JJ Reversible) (NNS reactions)) (VP (VBP are) (VP (VBN indicated) (PP (IN by) (NP (NP (JJ opposite-headed) (NNS kinds)) (PP (IN of) (NP (NNS arrows))))))) (. .)))
Reversible reactions are indicated by opposite-headed kinds of arrows.