BY R. GREIG-SMITH. 



285 



Influence of Reaction of the Medium. 



100 c.c. of medium 



Experiment 1, 





Experiment 2, 





of - c.c.N/1. 



Sulphuric Acid. 





Phosphoric Acid. 





Acid. 



Sodium 

 Carbon- 

 ate. 



Pea (K) 



Lupin 



(K) 



Robinia 

 (27°) 



French 

 Bean 



Pea 



(March) 



Macro- 

 zamia 



1-5 









11 















1-0 



— 



— 



— 



12 



5 



5 



4 



0-6 



— . 











— 



— 



— 



— 



0-5 



— . 



— 



— 



14 



7 



4 



7 



0-4 



— 



1 



2 



— 



— 



— 



— 



0-25 



— 



— 



— 



16 



6 



4 



9 



0-2 



— 



8 



10 



— 



— 



— 



- 



o-i 



— 



11 



11 



— ■ 



— 



— 



— 



o-o 



o-o 



14 



15 



16 



8 



9 



10 





o-i 



14 



15 











— 



02 



13 



15 



— 



— 



— 



— 



— 



25 



— 



— 



19 



8 



— 



10 



— 



0-4 



13 



15 



— 





— 



— 



— 



5 



— 



— 



20 



9 



14 



10 



— 



0-6 



11 



14 



— 



— 



— 



— 



— 



1-0 



— 



— . 



17 



8 



15 



10 



— 1-5 



— 



— 



12 



8 



13 



10 



Although the quantities of acid and alkali in the table are 

 expressed in terms of 100 c.c. of medium, the actual amounts put 

 into the 20 c.c. tests varied from - 01 to 0'3 c.c. The results 

 show that phosphoric acid is less injurious than sulphuric, and 

 also that the addition of an alkali, by conditioning an alkaline 

 and then faintly acid state of the medium, assists in the formation 

 of slime. The optimum quantity to add appears to be - 5 c.c. 

 of normal sodium carbonate to 100 c.c. of medium. It is 

 interesting to note that this amount is approximately what is 

 required to convert the phosphate into the tri-sodic salt. In 

 experiment 2, the reactions of the carbonated plates at the end 

 of the test were observed, and it was found that, with the- 

 exception of the Macrozamia race, which was neutral with 



