Given the situation described in the caption, I actually like how the toxicity at issue is not immediately intelligible. It parallels the fact that the actual toxicity of the ferns simply cannot be known without further inspection. But it could be interesting to include some sort of unsettling visual clue in the image that suggests there is underlying layer of risk, some way of inviting the viewer to think and look harder at this image to understand how it is conveying toxicity.
Perhaps playing with some sort of trope or cultural symbol associated with invisible risk or with not knowing whether you are currently at risk or not. Something like the Trojan Horse blended with Schrodinger's cat...
I'm not literally suggesting you should paste a "Trojan Cat" somewhere into the image like some kind of "Where's Waldo" game. To be honest, I don't really have a clear suggestion on how to achieve what I am suggesting. But it could be interesting to figure out how to work in something visual that represents/illustrates/hints at the undetectable level of radioactivity of these scrolls.
