Houghton Mifflin Company for the pictures from Sharp's "Year Out of Doors" on page [11]; "Riverside Natural History" on page [117]; Mill's "In the Beaver World" on pages [152] and [153].
Ginn and Company for the pictures from Breasted's "Ancient Times" on page [67]; "Agriculture for Beginners" on page [47]; Bergen's "Foundation of Botany" on pages [49], [190], and [197]; Bergen's "Elements of Botany" on pages [193] and [195]; Beal's "Seed Dispersal" on page [51].
U. S. Geological Survey for the pictures on pages [21], [22], [23], [30], [31], and [59].
New York Zoological Society for the pictures on pages [145], [159], and [216].
School Arts Magazine for the picture on page [221].
U. S. Department of Agriculture for the pictures on pages [125] and [189].
American Museum of Natural History for the pictures on pages [20], [24], [26], [139], and [162].
Cassell and Company for the pictures from "Popular History of Animals" on pages [118], [177], [179], and [217]; "Popular Science" on page [242].
Hutchinson for the pictures from "Marvels of the Universe" on pages [92], [101], [103], [141], [169], and [173]; "Marvels of Insect Life" on page [211].
The Dunham Company for the picture on page [45].