126 MASS. EXPERIMENT STATION BULLETIN 161. 



Four seedlings were placed in each bottle. As each experiment was 

 carried on in triplicate this gave a total of twelve seedlings for each treat- 

 ment. 



The first experiment was carried on with aluminum salt and red clover 

 seedlings. 



Treatment employed in First Experiment. 



1. Nutrient solution (check). 



2. Nutrient solution+10 c.c. Vio molecular solution of ammonia alum =216 parts 



per million of Al. 



3. Nutrient solution+5 c.c. Vi{> molecular solution of ammonia alum =108 parts 



per million of Al. 



4. Nutrient solution+2 c.c. Vio molecular solution of ammonia alum =4.3 parts 



per million of Al. 



5. Same as No. 2+CaO 1 



6. Same as No. 3+CaO } approximately .5 gram of CaO was added to each bottle. 



7. Same as No. 4+CaOj 



At the end of the first week quite marked differences were noticed in 

 the roots, while the tops of all but the check were about alike. The 

 roots of all but the check and No. 7 (43 p. p. m. Al + CaO) were very 

 much stunted. The roots consisted of the single taproot without root 

 hairs. Four days later the tops began showing differences similar to the 

 roots. The worst seedlings were those in the highest concentration of 

 aluminum, the conditions improving with a decrease in the amount of 

 aluminum present. The presence of the calcium oxide seemed to counter- 

 act the toxic effect in a marked degree but not entirely, except in the 

 most dilute solution. At the end of four weeks, when the experiment 

 was discontinued, the differences were the same as noted at the end of the 

 first week, only more pronounced. The seedlings in the bottles con- 

 taining 216 parts per million (No. 2) and 108 parts per milhon (No. 3) 

 of the aluminum, respectively, had died at the end of the third week, 

 even in those treated with calcium oxide. The check was in excellent 

 condition and No. 7 (43 p. p. m. + CaO) was fair. 



In the second experiment a series of cultures with ferrous sulfate was 

 added, and instead of using calcium oxide to neutralize the toxic action 

 of the aluminum salt the carbonate and sulfate were used in order to 

 avoid the danger of having the nutrient solution become alkaline from 

 the calcium oxide. Enough of the carbonate and sulfate was added to 

 make a saturated solution. 



Treatment employed in Second Experiment. 



1. Nutrient solution ] 



2. Nutrient solution+CaCOg ) checks. 



3. Nutrient solution +CaS04 J 



4. Nutrient solution+2 c.c. V\o molecular aluminum sol. =43 p.p.m. of Al. 



5. Nutrient solution+2 c.c. Vxi) molecular Al sol.+CaCO;;. 



6. Nutrient solution+2 c.c. ^Ao molecular Al sol.+CaSO^. 



7. Nutrient solution+1 c.c. -Vio molecular Al sol. =21.6 p.p.m. of Al. 



8. Nutrient solution+1 c.c. ^Ao molecular Al sol.+CaCOs. 



