I’m not sure why army1987 retracted his comment,
On the last panel (that for hypericum) of the figure on the NatGeo page the red curve doesn’t look like the negative derivative of the gray curve, so I assumed I was missing something.
On the last panel (that for hypericum) of the figure on the NatGeo page the red curve doesn’t look like the negative derivative of the gray curve, so I assumed I was missing something.