1908] OSTERHOUT— ACTION OF MAGNESIUM AND POTASSIUM 123 



(e. g., leaves and stems) which are raised above them. It seemed 

 desirable therefore to find out how sections of stems and roots would 

 behave in the solutions. The answer to this question is given in 

 Table VII. Transverse sections of the stem of Tradescantia and the 

 root of the common red beet were employed. They were cut on a 

 microtome and were of considerable but uniform thickness. 



TABLE VII 



Cuttings and Sections 



All quantities given are cubic centimeters of .0937W solutions 



CtTLTURE SOLUTION 



Duration of life in days 



Microtome sections 



of stem of 

 Tropaeolum majus 



Microtome sections 



of root of 



Beta vulgaris 



Development 



Cuttings is<=°> 



long of 

 Tradescantia 



KCl 



100 KCl ) 

 40 MgCU 5 ' 



MgCl, 



Distilled water 



20 



28 + 



20 

 28 + 



14 



27 



18 

 28 + 



No roots 



Short roots 



No roots 

 Long roots 



A plus sign indicates that the plants were alive at the end of the experiment. 



In both cases the color and microscopic appearance served as the 

 criterion of death. As is seen in Table VII, the results agree with 

 those already obtained. The table likewise shows the results obtained 

 from cuttings of Tradescantia (about 15'^'^ long) which were placed 

 with their lower ends in the solutions. 



In view of the striking agreement of results obtained from such a 

 variety of material, it seems useless to seek for further proof. The 

 experiments of Loew and Aso also show antagonism between potas- 

 sium and magnesium, as far as they go. They do not, however, 

 employ sufficient potassium (nor sufficiently strong solutions) to bring 

 out the results clearly. The use of percentage solutions (rather 

 than molecular solutions) likewise obscures their results. More funda- 

 mental is their confusion of physiologically balanced solutions with 

 ordinary nutrient solutions.^ 



As for the theory of Loew and Aso that the inhibitory action of 

 potassium on magnesium is due to the formation of a double salt; I: 



s Cf. OsTERHOUT, On nutrient and balanced solutions. University of California 

 Publications, Botany 2:317. 1907; also, BoT. Gazette 44:259-272. 1907. •* ' .*. 



