84 MASS. EXPERIMENT STATION BULLETIN 339 



placed in each crock; 5 crocks were used per treatment. Plants were of the 

 variety Rubel. Treatments were as follows: sulfur 1, 2, 4, 8 gms. per crock; 

 aluminum chloride, 5, 10, 20, 40 gms.; aluminum sulfate, 7, 14, 28, 55 gms.; 

 citric acid 62, 125, 250, 500 cc. of molecular solution per crock; hydrochloric 

 acid 62, 125, 250, 500 cc. of normal solution; orthophosphoric acid (H 3 P0 4 ) 

 62, 125, 250, 500 cc. of normal solution; and lime 5, 10, 20, 40 gms. per crock. 

 The following statements are based on this year's results with the soil used. 



1. H3PO4 gave the best growth of plants of any of the chemicals tried. 



2. Aluminum sulfate and sulfur were about equally effective in producing 

 soil acidity and produced about equal growth response, but previous experi- 

 ments show that too much sulfur may injure the plants. 



3. Aluminum chloride did not increase acidity as much as aluminum sulfate 

 and reduced the growth of the plants. 



4. Citric acid reduced rather than increased acidity and reduced the growth 

 of plants. 



5. HC1 in all concentrations was toxic to the plants. 



6. Lime in all amounts used appeared to reduce the growth of plants. 

 During 1936 the work on the chlorosis of blueberry plants was continued. 



Several different chemicals, some as sprays and some as soil amendments, 

 were applied to affected bushes. Ammonium sulfate was the only one of these 

 to which the plants showed a definite favorable response. A preliminary report 

 of this work will appear in the Annual Report of the American Society for Horti- 

 cultural Science for 1 936. 



Blueberry Culture. (J. S. Bailey.) In the spring of 1936 an experiment 

 was started in cooperation with Dr. Frank Shaw of the Department of Ento- 

 mology to test the effectiveness of honey bees as pollinators for highbush blue- 

 berries and also to observe the insects which visit blueberry bushes exposed to 

 open pollination. A cage 5' x 10' x 10' was placed over one bush each of the 

 varieties Harding and Pioneer and another over the varieties Pioneer and 

 Grover. A branch of each bush was covered with cheesecloth to exclude bees. 

 A nucleus hive of honey bees was placed in each cage. Counts of the berries set 

 gave the following: 



Number of fruits set 

 Variety With bees Without bees 



Harding 42 



Pioneer 16 



Grover 36 



Pioneer 32 3 



The set of fruit on the caged bushes was as good as that on bushes exposed 

 to open pollination. 



Collections of all insects visiting blueberry bushes were made at different 

 hours of the day from May 21 to May 26. The following table lists those insects 

 which have been identified: 



Bumble bees Solitary bees Honey Bees 



Bombus impatiens 23 Colletes 22 56 



Bombus perplexus 45 Halictus 20 — 



Andrena 30 



Total 68 72 56 



