Sentence:  Drawings and pictures are more than <WSD>mere</WSD> ornaments in scientific discourse. Blackboard sketches, geological maps, 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:  Just, only; no more than (from 16thc.), pure and simple, neither more nor better than might be expected.