in Thoreau’s Journal:

When I look out the window, I see that the grass on the bank on the south side of the house is already much greener than it was yesterday. As it cannot have grown so suddenly, how shall I account for it?

I suspect the reason is that the few green blades are not merely washed bright by the rain, but erect themselves to imbibe its influence, and so are more prominent, while the withered blades are beaten down and flattened by it.