June 30th, 1921 
Vol. XX, No. 2 
THE 
NEW PHYTOLOGIST 
A BRITISH BOTANICAL JOURNAL 
EDITED BY 
A. G. TANSLEY, M.A., F.R.S. 
UNIVERSITY LECTURER IN BOTANY 
CAMBRIDGE 
IN CONSULTATION WITH THE 
THE CAMBRIDGE BOTANY 
CONTENTS 
Permeability. By Walter Stiles . 
Stomata and Hydathodes in Campanula rotundifolia L., and their relation 
to environment. By Margaret W. Rea, B.Sc., Queen’s University, 
Belfast. (With 6 figures in the text) . . . . . . . 56 
The Hydrion Differentiation Theory of Geotropism: a reply to some 
criticisms. By James Small. 73 
The Grouping of Vascular Plants. By Margaret Benson. (With Diagram) 82 
Note on a Numerical Sequence of Plant Families. M. Benson ... 90 
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