1913] SHULL—SEMIPERMEABILITY OF SEED COATS 183 
lifeless membranes forming the coats of seeds frequently exhibit 
osmotic effects. A number of widely separated families are repre- 
sented in the list now known to possess such properties: Alismaceae 
(Alisma Plantago-aquatica), Gramineae (barley, wheat, oats, etc.; 
probably most grasses), Chenopodiaceae (sugar beet), Rosaceae 
(peach, apple), Leguminosae (Vicia Faba, scarlet runner, lima bean), 
Compositae (Xanthium, Helianthus annuus). It should be said at 
once that these seeds do not all exhibit the same degree of semi- 
permeability. The coat of Xanthium apparently permits no passage 
or only very slow passage of certain solutes, comparing favorably 
with the coats of Hordeum and Triticum in this respect. Coats of 
the sunflower and peach are only less efficient, while the bean coats 
usually allow a noticeable passage of salts. ‘The Leguminosae seem 
to be less uniform in their behavior than any seeds tested. Certain 
specimens have very good serps Teean es membranes, others have 
rather poor ones. 
As pointed out in the introduction, ATKINS found Leguminosae 
not to possess semipermeable testas, but had overlooked the open 
micropyles. Direct methods of testing proved that these mem- 
branes do act osmotically. It was not found practicable to wax 
these membranes onto rubber corks, because the great amount of 
expansion of the membrane on soaking, after the apparatus was 
arranged, always resulted in breaking the coat loose from the wax. 
To overcome this difficulty, the wet bean coats were placed tightly 
between two perforated rubber corks which were smeared slightly 
with vaseline, and used just as in the case of Xanthium already 
described. In this case the hole in the cork below the membrane 
must also be carefully filled with water to insure contact of both 
fluids with the membrane. 
Coats of Vicia Faba used with saturated NaCl solution gave a 
rise of 72 mm. in 36 hours; and of scarlet runner a rise of 135 mm. 
in to days, the rise continuing throughout this time, but amounting 
to only 17 mm. during the last 4 days.. The escape of the salt 
through the coats of both these legumes was readily demonstrated 
by use of AgNO,. 
It is a pleasure to recird the fact that Professor STEVENS of the 
University of Kansas has for more than 8 years been using the coats 
