64 



PAUL J. ANDERSON 



various strengths of sugar solutions were used in a solution of 

 the cement dust 1-170 (i.e., 1 g. of dust to 170 cc. of water). The 

 results are given in Table IV. 



During the blooming season of 1911 the expermients were re- 

 peated with pollen which matured naturally on the trees. The 

 results practically duplicated those given above. The writer has 

 not been able to explain satisfactorily the low percentage of 

 germination in the checks. A possible explanation is that they 

 required an acid solution, while we were using a neutral one. 

 No germination whatever was secured in the cement dust 

 solution. 



TABLE V 

 Shoivs apple pollen germination. Counted after eighteen hours 



Pear pollen. Better success was obtained in artificially ger- 

 minating the pollen of pears. Solutions of 20, 22 and 25% sac- 

 charose were used and between 65 and 75% germination was 

 constantly secured in the checks but none at all in the 1-100 

 cement dust solution. 



Apple pollen. This was the most satisfactory set of experi- 

 ments. The blooming season of the apple is longer and gave more 

 opportunity for an extended set of experiments. Table V shows 

 the results of tests where various concentrations of saccharose 

 were used. The optimum concentration, as indicated here, was 

 10%. This concentration was therefore used in the further tests. 

 Germination in the dust solution of 1-100 was practically nil. 



