in Thoreau’s Journal:

I looked again on the forest from this hill, which view may contrast with that of last Sunday. The mist produced by the leafing of the deciduous trees has greatly thickened now and lost much of its reddishness in the lighter green of expanding leaves, has become a brownish or yellowish green, except where it has attained distinctness in the light-green foliage of the birch, the earliest distinct foliage visible in extensive great masses at a great distance, the aspen not being common. The pines and other evergreens are now fast being merged in a sea of foliage.