Sentence:  Drawings and pictures are more than mere ornaments in scientific discourse. Blackboard sketches, geological <WSD>maps</WSD>, diagrams of molecular structure, astronomical photographs, MRI images, the many varieties of statistical charts and graphs: These pictorial devices are indispensable tools for presenting evidence, for explaining a theory, for telling a story. 
Meaning of the word marked with <WSD> tags:  A visual representation of an area, whether real or imaginary.