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PREFACE TO THE THIRD EDITION 
Chapter VIII on “Taxonomy” has been increased by seven pages 
of new data, and the whole former text carefully revised. 
Chapter IX on “Ecology” has been newly introduced as has also 
a Glossary of Botanical Terms. The index has been so planned as 
to make the information contained in this book readily accessible. 
To the authors of works from which cuts were borrowed the 
writer’s thanks are due. 
H. W. Y. 
