Learners build models to learn about the special cells and structures that plants use to move water from their roots up through the stems and leaves. The celery-in-colored-water demonstration serves as the basis for their models. Learners use paper towels to model how leaves evaporate moisture into the atmosphere, and fill straws with paper towels to model how plant stems carry water from the earth to the leaves. They construct two models, with a large leaf and a small leaf, and measure how much the different leaves allow to evaporate overnight. The lesson plan includes handouts, background information, and suggested extension activities.