DOUBLE NUMBER. 
VOL. XIX, Nos. 9 & 10. NOV. & DEC., 1920. 
[Published January 31st, 1921.] 
THE 
A BRITISH BOTANICAL JOURNAL, 
EDITED BY A. G. TANSLEY, M.A., F.R.S. p* /' 
L\;V ' *'* . t . • * * - \ ' •V.p'*. .L] : •;/; • 1 
UNIVERSITY LECTURER IN BOTANY, CAMBRIDGE, 
IN CONSULTATION WITH THE STAFF OF THE CAMBRIDGE BOTANY SCHOOL 
Contents: 
1 
MUTATIONS AND EVOLUTION. Chapter VII.-XIL - . R. Ruggles Gates. 
NOTES ON FRESHWATER ALCLE. I— IV. [With Two 
Figures in the Text] 
W . J\ Hodgetts. 
PLANT FAMILIES: A PLEA FOR AN INTERNATIONAL 
SEQUENCE.- Alfred Gander sen. 
■ 
THE EVOLUTION OF PRIMITIVE PLANTS FROM THE 
GEOLOGIST’S VIEWPOINT - - - * - Charles Schuchert. 
PRELIMINARY NOTE ON A HYDRION DIFFERENTIATION 
THEORY OF HELIOTROPISM - - ... - - James Small. 
REVIEW. “ FOSSIL PLANTS” (Seward) .... W.N.E. 
: ' ' 
WILLIAM WESLEY & SON, 
- 
28 Essex Street, Strand, W.C.2. 
LONDON. 
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