Plastic ziploc sandwich bags

 Duct tape

 Scale (that can be zeroed)

 Trees

 Paper towels

 Label plastic bags

 Weigh plastic bags, separately

 Find a tree where students can easily reach leaves

 Carefully place entire leaf inside bag and zip as much as possible and then duct tape to seal

 Place some bags on leaves in shade and some in sunlight and time for twenty minutes

 Make sure that you take measurements from several leaves in both sunlight and shade

 Collect leaves and weigh entire bag including leaf and duct tape

 Weigh duct tape

 Weigh leaf, after patting dry with paper towel

 Subtract weights of leaf, duct tape, and 1^st weight of bag from total bag weight

 Graph results in mg H₂O/mg leaf/hour