in Thoreau’s Journal:

How much of beauty–of color as well as form–on which our eyes daily rest goes unperceived by us! No one but a botanist is likely to perceive nicely the different shades of green which the open surface of the earth is clothed–not even a landscape painter if he does not know the species of sedges and grasses which paint it.  

August 1, 2009 at Cook Intervale, Sandwich, New Hampshire