392 BOTANICAL GAZETTE [MAY 
remnants of the original ovary wall, the integuments, and the 
epidermis of the nucellus (14, 32). This coat cannot be removed 
from the endosperm and embryo without injury, and thus attention 
must be called to the difficulties which are immediately encoun- 
tered in studying the coat effects of the oat. To know absolutely 
what the coat effects are is impossible; for to break the coat 
involves dangers of “wound effects,” or of infection; while if the 
seeds are subjected to fluids or gases, it cannot be said with cer- 
tainty that any results obtained are due primarily to the external 
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Fic. 1.—Water intake, showing semipermeability of the wild oat; increments 
in percentage of air dry weight; in water, solid line; in gram-molecular sodium 
chloride solution, broken line. 
agents used, as questions of their actual entry to the embryo arise, 
and also the question as to what exact physiological function 1S 
set in action by such agents, even if they are successful in forcing 
germination. These difficulties are of course obviated in expert 
mentation with seeds which, like Xanthium (60), permit of an sy 
removal of the seed coat. However, in a study of Avena it 1S 
necessary to gather as much data as possible from a variety of 
external factors, and, recognizing the uncertainty to which any one 
line of inquiry alone leads, to judge the situation from the combined 
results. 
