1918] Waynick: Antagonism and Cell Permeability 163 



To define normal permeability is very difficult. There seems to 

 be a comparatively wide range of concentration of salts over which 

 the amount of any element taken up may vary without affecting the 

 growth of the plant to any considerable extent. There is Likewise a 

 wide range over which the ratio of any one clement to any other may 

 change without being detrimental to plant growth. The hitter point 

 has been discussed above in connection with a possible optimum 

 calcium-magnesium ratio for plants. The first point referred to has 

 been very well treated by Gile and Ageton, 00 so that further reference 

 need not be given here. 



For the work in hand the percentage composition of the plants 

 grown in the control cultures seemed to be the most logical criterion 

 of normal permeability available. There are variations between the 

 controls as regards composition, but they are relatively small. On 

 the other hand, the percentages of magnesium, for instance, range 

 from .02 per cent to 9.21 per cent, depending upon the solution used. 

 The percentages of calcium differ over a wide range as well. From 

 the data presented there can be no doubt whatever thai the composi- 

 tion of the plant, as regards inorganic constituents at least, may be 

 altered enormously by variations in the surrounding solution. 



That portion of the root system in any plant which functions as a 

 semipermeable membrane is obviously of greatest importance in a 

 study of the present kind. The actual area of the membrane which 

 is in contact with the solution must be known in every case before it 

 can be said that the permeability of one root system is greater than 

 that of another. The actual area of the plasma membrane cannol he 

 measured directly because, in the first place, we have no means of 

 determining just how much of the root is involved, and secondly, the 

 area concerned may be changing continually. 



Length of the roots and their number and length together as well 

 as green weight and dry weight have been taken as criteria of the 

 existence of antagonism. In the present paper the dry weighl has 

 been taken as proportional to the area of the plasma membrane 

 through which salts may enter the plant. It cannot be stated defi- 

 nitely that the two are proportional. They have only been so con- 

 sidered since the dry weight of the plant was the most logical criterion 

 to employ. The reservation must always be made that the two may 

 not be directly proportional, even though they are treated as being so. 



That the permeability of the plasma membrane of the plant cells 



so Porto Rico Agr. Exp. Sta. Bull. 16, 1914. 



