Vol. XXXV. No. CXXXIX. July, 1921. 
Price 15s. net. 
LATELY HONORARY KEEPER OF THE JODRELL LABORATORY, ROYAL BOTANIC GARDENS; KEVV 
■ / -k 
JOHN BRETLAND FARMER, D.Sc., M.A., F.R.S. 
PROFESSOR OF BOTANY, IMPERIAL COLLEGE OF SCIENCE AND TECHNOLOGY, LONDON 
FRANCIS WALL OLIVER, M.A., D.Sc., F.R.S. 
QUAIN PROFESSOR OF BOTANY, UNIVERSITY COLLEGE, LONDON 
AND 
ROLAND THAXTER, M.A., Fh.D. 
PROFESSOR OF CRYPTOGAM I C BOTANY IN HARVARD UNIVERSITY, CAMBRIDGE, MASS., U.S.A. 
ASSISTED BY OTHER BOTANISTS 
LONDON 
HUMPHREY MILFORD, OXFORD UNIVERSITY PRESS 
AMEN CORNER, E.C. 
Edinburgh, Glasgow, New York, Toronto 
Melbourne, Cape Town, and Bombay 
1931 
Printed in England at the Oxford University’ Press. 
