54 CARNEGIE INSTITUTION OF WASHINGTON. 



O.OOIn it was found that hydroxides of all of the metals increased the 

 hydration capacity of agar. This was of importance, as a review of all 

 available data seems to show that the range of the H"*" — 0H~ 

 balance in the plant-cell lies between the values expressed by Phs and 

 Phu, or between about 0.01m aspartic, succinic, or propionic acid and 

 under O.OOIn KOH. 



The reversal of effects at great attenuations in the hydroxides led 

 to the extension of auxographic measurements upon the effects of low 

 concentrations of the salts which are of such interest and importance 

 in cultures, and the action of chlorides, nitrates, and sulphates of potas- 

 sium, calcium, sodium, and magnesium upon agar, gelatine, and mix- 

 tures was made at Carmel in the summer of 1920. The action of these 

 reagents upon living and dead cell-masses was also tested late in the 

 summer of the same year. The principal results of the entire series 

 of experiments may be summarized as follows: 



The strong metallic bases, which were found to lessen the swelling 

 of agar to a degree corresponding to their relative positions in the elec- 

 tromotive series when used as hydroxides, give the same relative action 

 when used as chlorides. The series runs Ca, K, Na, the greatest 

 retardation being affected bj^ the calcium and the least by sodium when 

 used at concentrations of 0.01m. 



Reversed effects by which hydration of agar is increased are shown 

 by the hydroxides at O.OOIn, as described in a previous contribution, 

 but no well-defined differences among the bases used could be made out. 

 Similar reversed effects were exhibited by the chlorides of calcium, 

 magnesium, potassium, and sodium at 0.0001m and by potassium and 

 sodium in concentrations as great as 0.001m. 



Purified agar used in the experiments has a Ph value of 6.5, also 

 swells more in HCl at a Ph value of 4.2 than in water, a statement 

 be applied in correction of various conclusions in previous papers. 



Purified agar shows exaggerated swellings in a series of acid, salt, 

 and hydroxide solutions in which the hydrogen-ion concentration ranges 

 from Ph 4.2 to 11. 



Purified agar also shows exaggerated swellings in sodium and potas- 

 sium nitrates at 0.0001m, but not in the sulphates. 



Of the chlorides of calcium and potassium and hydrochloric acid at 

 concentrations from 0.01m to 0.0001m only KCl at 0.001m and 0.0001m 

 increase the swelling of an agar-gelatine mixture. In a similar series 

 only KCl at 0.0001m increases swelling in a gelatine-agar mixture. 



Agar plates with included chlorides at concentrations increasing 

 swelling, when applied as hydrating solutions, showed exaggerated 

 swelling in HCl, NaCl, KCl at 0.0001m, but a lessened swelling in 

 CaCl2 and MgCl2 at this concentration. 



Gelatine plates, with incorporated salts as above, showed swelling 

 in HCl increasing with the concentration beginning with the 0.001m 



