THE 
NEW PHYTOLOGIST 
Vol. XXI, No. 3 June i, 1922 
PHYSIOLOGICAL STUDIES IN PLANT 
ANATOMY 
III. THE STRUCTURE OF THE ENDODERMIS 
IN RELATION TO ITS FUNCTION 
By J. H. PRIESTLEY and EDITH E. NORTH 
CONTENTS 
PAGE 
Introduction . . . . . . 113 
Preparation of the Endodermis by Maceration . 114 
Developmental Stages of the Endodermis . . . 116 
The Primary Endodermis . . . . . . 117 
(1) Its Micro-chemical Structure . . . . 117 
(2) The Casparian Strip . . . . . n8 
(a) Impregnating Substances of the Casparian Strip 120 
(b) Basal Substances of the Casparian Strip . . 123 
(3) The Function of the Primary Endodermis . . 124 
The Secondary Endodermis . . . . . . 125 
(1) The Suberin Lamella . . . . 125 
(2) The Undulation of the Casparian Strip . . 131 
(3) The Function of the Secondary Endodermis . 132 
General Discussion . . . . . . 135 
Summary . . . . . . . 137 
References ......... 138 
Introduction 
apart from the Lycopodiaceae (Mager(i 5 )) the endodermis is 
/i typically present in the roots of all vascular plants and it is 
frequently present in the stem also. We have been led to re-investigate 
the structure and functions of this layer of cells as the result of a 
conviction that it plays a very important part in the exchange of 
water and solutes between the tissues on either side of it. This role 
has been assigned to the endodermis in an explanation recently 
advanced of the phenomena of exudation pressures in plants 
(Priestley (20), Priestley and Armstead (22)). 
Phyt. xxi. III. 
8 
