Variation in the contact angl e of water on the cuticle of the growing leaf was measured, and the results were shown as follows: 1) The contact angle on the leaf of Euonymus radie a ns Sieb. became larger with the progress of leaf expansion. 2) The contact angle o n the leaf of Prunus donarium Sieb. var. spontanea Makino was relatively large when the leaf was young and not yet expanded but the angle diminished with the beginning of the expansion of leaf, and enlarged again with the completion of the leaf expanding.