DIRECTOR OF THE JOHN INNES HORTICULTURAL INSTITUTION, HON. FELLOW OF ST. JOHN'S COLLEGE, CAMBRIDGE, AND FORMERLY PROFESSOR OF BIOLOGY IN THE UNIVERSITY
WITH ILLUSTRATIONS
New Haven: Yale University Press
London: Humphrey Milford
Oxford University Press
MCMXIII
Copyright, 1913
By Yale University
First printed August, 1913, 1000 copies
THE SILLIMAN FOUNDATION