22 



TECHNICAL BULLETIN 17 



n/5 H 3 PO 4 to give a series of hydrogen-ion concentrations ranging 

 from pH 2.4 to pH 12. The pH value of the solutions was deter- 

 mined colorimetrically, except for the highest three alkaline solutions 

 for which the theoretical value according to the curve is given. Spores 

 from a seven-weeks-old barley head culture were dusted over the 

 surface of the solutions in Syracuse watch glasses. The percentage 

 of germination was determined after 18 hours and after 36 hours. 

 Similar series were run in triplicate at 19, 24, and 32 C. The 

 results are given in Table VIII. 



TABLE VIII 



SPORE GERMINATION OF H. sativum IN H 3 PO 4 KOH SOLUTIONS OF VARIOUS HYDROGEN-ION 

 CONCENTRATIONS AT DIFFERENT TEMPERATURES 



PH 



Hours 



19 C. 



Germination 

 24 C. 



32 C. 



* Theoretical value according to Clark and Lub's titration curve for ortho-phosphoric 



acid. 



