Three volume collection Nature Library - these books are numbered I, II, III, and are complete in themselves, though I can't find any note of how many volumes were in this set originally.
These are different authors and illustrators / photographers, original copyright dates turn of the century. Topics are birds, butterflies and moths, trees, moss and lichens. Illustration styles vary topic to topic, but all have many illustrations - some color plates, some line drawings, some black and white photography.
These have beautiful covers, marbled hardboard with leather or leatherette spines and corners. Size is about 9 1/4" x 7 1/4" x 2" thick. All are in good condition, complete, not dog eared or marked up.