

374 BOTANICAL GAZETTE [may 



must not be underestimated. That they perform great physiolog- 

 ical functions is coming to be recognized more and more as our 

 knowledge of them increases. 



The cell wall may be thought of as a non-living membrane, and 

 its functional importance is emphasized by the work of Hansteen- 

 Cranner (16), in which it is indicated that the antagonism of 

 Ca" for Mg" in root toxicity, the action of Ca" in increasing 

 transpiration and decreasing absorption, and the action of K" in 

 decreasing transpiration and increasing absorption, is due funda- 

 mentally to the effect of these ions upon the cell wall. The impor- 

 tance ascribed by Wachter (30) to the cuticle and cork of the 

 outer layers- of the beet in preventing the loss of sugar also may 

 be pointed out. Other investigators (4, 10) have shown that the 

 non-living coat plays a dominant role in seeds, the coat character 

 being an important factor in determining the respiration, water 

 intake, entrance of toxic materials, delay in germination, longevity, 

 protection from leaching of stored materials, and from mechanical 



injury, etc. 



membranes 



in itself, and it was hoped that results so obtained would throw 

 light upon the problem of the permeability of plant membranes 

 in general. In this connection we quote Pfeffer (24): "the 



will first have to deal with 



mental 



perhaps in 



make clear processes taking place in th 

 living semipermeable plant membrane 

 r Brown (5) in the barley grain, and h 



7? 



in 1907 by Brown (5) in the barley 

 Worley (6) measured its permeability to water. Schroeder 

 (27) reported a similar membrane in the wheat grain. Gola (13) 

 found such membranes in the seeds of a great many different 



species. 



measure 



of the membranes to water. Shull (28) found that the seed coat 



permeable to certain substances, and pointed 

 r antage this membrane had for experimental 



sem 



purposes, in that it could be remo\ 



meability characters studied directly, without other structures 

 becoming factors in the experiment. He constructed an osmometer 



^ 



