THE EFFECT OF CEMENT DUST 67 



An extremely small amount of lime is evidently sufficient then 

 to prevent germination. The writer had hoped to test out all 

 the other constituents of the dust but has not found opportunity 

 to do so. It is possible that other substances in the dust may 

 go into solution in the acid stigmatic secretions to an extent suf- 

 ficient to prevent pollen germination. Whether this be so or not, 

 it is certain that the injury from the lime alone is sufficient to 

 account for the damage. 



Work of Professor Beach. There should be mentioned at this 

 point the work of Professor Beach^ who investigated the effect 

 of spraying fruit trees in bloom. Artificial germination tests in 

 the laboratory were used here also. Two paragraphs are quoted 

 from Professor Beach's bulletin in which are given the results 

 of his investigation. 



From page 433 of that bulletin : 



From these investigations it appears that if before pollination occurs, 

 the stigmatic surface of the pistil should be covered either \\dth bor- 

 deaux mixture alone or with arsenical poison alone, of the strength com- 

 monly used in spraying orchards, there would be no germination of 

 any pollen which might afterwards reach the stigmatic surface and so 

 fertilization would be prevented and no fruit would be formed. Even 

 the presence of lime alone, of the strength commonty used in spray mix- 

 tures, prevented the germination of pollen. Bordeaux mixture was di- 

 luted in aqueous sugar solution to 500 parts, 200 parts, 100 parts, 50 

 parts, 2 parts, and 1 part in 10,000 of culture media into which various 

 kinds of pollen were introduced. Even when diluted to 50 parts in 

 10,000 it prevented germination to large extent and where germination 

 (lid occur the growth which followed was decidedly slow and the pollen 

 tubes were dwarfed. When diluted to 100 parts, 200 parts, or 500 

 parts either no germination or practically none was found. 



Also on page 442: 



In the tests where the trees were sprayed repeatedly during the 

 blooming season so as to hit as many as possible of the new blossoms 

 which opened from day to day, but very few blossoms survived the 

 treatment and consequently but little fruit set. This shows that the 

 ordinary spray mixtures surely prevent the setting of fruit when applied 

 to the blossoms soon after they open. 



1 Beach. S. A. and Bailej^ L. H. Spraying in bloom. New York (Geneva). 

 Agr. Exp. Sta. Bull. 196. 1900. 



