The Structure of the Integumentary System of the 
Barley Grain in Relation to Localized Water Ab¬ 
sorption and Semi-permeability. 
BY 
E. J. COLLINS. 
With four Graphs, nine Figures, and one Key Figure in the Text. 
Contents. 
PAGE 
Section i. Introduction.381 
Section 2. Structure and Reactions of the Investing Integumentary Layers : 
(a) Morphology and structure of the layers ......... 383 
(b) Reaction of the various parts of the integumentary system to reagents . . . 385 
(c) Possible alteration of the membrane by penetrating substances ..... 387 
(d) Extent of the cuticularized membranes.388 
(e) Impermeability of the cuticular membrane of the tegmen to solutes .... 389 
(/) Summary.389 
Section 3. Location of the Uptake of Water by the Barley Grain : 
(a) General. 
(b) Uptake by germinal and apical portions of the grain compared .... 
(i c ) Degree of permeability of the cuticularized integument to water 
( d ) Efficiency of the superficial structures of the grain in capillary conduction of liquids 
Section 4. Location of the Uptake of Solutes by the Grain : 
(a) Uptake of iodine' and its distribution in the grain. 
(b) Uptake and distribution of some acids. 
( c ) Uptake of stains. 
• 39 ° 
• 39 2 
• 396 
• 39 8 
• 399 
. 404 
. 406 
Section 5. The Spread of Enzymes on Germination and the Path of Liquid 
Penetration ..... . . 
408 
Section 6. Discussion of the Possible Paths of Easy Penetration in the 
Germinal Region of the Grain. . 
Conclusions.. 
Bibliography.. 
410 
412 
4 T 4 
Section I. Introduction. 
T HE integumentary system of the cereal grains is a morphological com¬ 
plex resulting from the more or less complete fusion of the various 
units in the system with each other. In the so-called naked grains the 
seed-coats and pericarp together form the investment, whilst in the ordinary 
varieties of barley the flowering glumes are included. As the maturation 
of the grain proceeds, the system dries and becomes membranous. 
(Annals of Botany, Vol. XXXII. No. CXXVII. July, 1918.) 
