1930s vintage natural history books w/ color plates, butterflies, trees, flower illustrations

Set of four shabby but pretty books from the Nature Library series, dated 1930. There's four volumes here - Garden Flowers, Wild Flowers, Trees, Butterflies. All have lovely color illustrations! The color plates measure about 8 1/2" x 6" overall.

The books themselves have soil and wear (spots and staining to page edges, some water browned marks. They're free of any musty of moldy smells, though - and they'd make OK reading copies.