Many years ago it was taught that plants and animals were composed of different materials: plants, of a chemical substance of three elements,- carbon, hydrogen, and oxygen; animals of one of four elements, nitrogen being added to the other three.

Neither Darwin nor Wallace attended the meeting. On his second trip through the American west he and Hooker reportedly collected over 1000 specimens. In 1859 he was elected a foreign member of the Royal Swedish Academy of Sciences [2].

This book known simply as Gray's Manual has gone through a number of editions with botanical illustrations by Isaac Sprague and remains a standard in the field. Of Gray's many works on botany the most popular was his Manual of the Botany of the Northern United States from New England to Wisconsin and South to Ohio and Pennsylvania Inclusive. Asa Gray (November 18 1810 – January 30 1888) is considered the most important American botanist of the 19th century.