The inscription on this leaf is Qur'an, sura xvii, al-isra' (bani Isra'il), v. 80.
An almost identical but unsigned leaf, identified as Spanish chestnut (castanea sativa), and with the same inscription, is published in the catalogue of the recent exhibition of highlights from the Aga Khan Trust (Spirit and Life. Masterpieces of Islamic Art from the Aga Khan Museum Collection, exhibition catalogue, London, 2007, no. 20, p.15). That entry describes the calligraphic composition as 'resembling a boat filled with a crew, their long oars dipping into the water that is the skeleton of the leaf' (The Aga Khan Trust, op. cit., p. 44).