VOLUME LVI NUMBER 3 
fe se 
BOTANICAL GAZETTE 
SEPTEMBER 1913 
SEMIPERMEABILITY OF SEED COATS 
CONTRIBUTIONS FROM THE HULL BOTANICAL LABORATORY 176 
CHARLES A. SHULL 
(WITH NINE FIGURES) 
I. Introduction 
As our knowledge of the physical and chemical characteristics of 
seed coats increases, the importance of the physiological rdle and 
the biological significance of these structures become more and more 
apparent. Much work has been done upon the germination of 
seeds without an adequate knowledge of the real conditions offered 
to the embryos for their development. Many chemical substances 
and various ethereal stimuli have been used to influence the 
germination of seeds, and as a rule the seeds have been used with 
coats intact. This has been true especially of the Germans who 
belong to the vitalistic school. The assumption has been that the 
coats of seeds, and cell walls generally, are permeable to practically 
all water-soluble substances, and that the dead membranes and cell 
walls do not modify ethereal and chemical stimuli which act through 
- them, simply because they are dead. 
Recently a number of papers have appeared which have a very 
important bearing upon these problems. In 1907 Brown (10) 
reported the discovery of a semipermeable membrane forming the 
outer layer of the seeds of Hordeum vulgare var. coerulescens, and 
later (11) published an account of the selective permeability of this 
outer dead membrane of the seed. This work was followed by 
169 
so 
