Water stored within the tree and released to the transpiration stream was considered as a possible explanation for a discrepancy between two independent estimates of evaporation from a Pinus sylvestris L. plantation in Thetford Chase, East Anglia. A technique is described by which an estimate is made of the quantity of stored water. Trees were allowed to transpire only stored water and estimates made of the quantity available. The results showed, however, that the amount of water available from store is insignificant and could not account for the discrepancy between evaporation estimates.