498 



AMERICAN JOURNAL OF BOTANY 



[Vol. 8, 



and the colonies were counted. Results from two of several tests are shown, 

 giving the averages (see table 18). 



2. ioo mg. of Easter lily pollen was ground well with sterile sand, then 

 well shaken with ioo cc. of 0.85 percent NaCl and 100 mg. of thymol. 1 cc. 

 of this suspension was diluted with 100 cc. sterilized water. Plates of agar 

 were poured with 1 cc. of this dilution and incubated 24 hours at 30 . The 

 average number of colonies on 4 plates was 3. The experiment was repeated, 

 omitting thymol, and the average number on 4 plates was 12. Similar 

 tests with corn, ragweed, and rye gave corresponding results. Thymol 

 does exert an inhibiting action but does not prevent growth of bacteria 

 introduced with the pollen. 



3. One gram each of corn, ragweed, rye, and Easter lily pollen was 

 ground with sterile sand and extracted 24 hours in the ice chest with 100 cc. 

 of 0.85 percent NaCl. This solution was filtered through a small, thor- 

 oughly sterilized Berkefeld filter into a sterile side-neck flask. Care was 

 taken to plug the side-neck with cotton before sterilizing so that no con- 

 tamination could enter while filtering by suction, i-cc. portions of each 

 filtrate were removed with a sterile pipette and agar plates were poured, 4 

 of each kind of pollen. These were incubated at 37 for 48 hours. No col- 

 onies appeared. All the plates were sterile. Six days later one plate had a 

 colony of mold, but this could easily have been later contamination. The 

 sterile filtered extracts were then used for testing for diastase, liquefaction 

 of gelatin, and digestion of fibrin. The diastatic action seemed as rapid as 

 before filtration, but the gelatin liquefaction and fibrin digestion were de- 

 creased. The gelatin was completely liquefied after 48 hours, and the rye 

 and ragweed extracts caused only slight digestion of the fibrin. Repeti- 

 tion with other samples confirmed the belief that the filter absorbed the en- 

 zyme to a considerable extent. If one could use separate filters for each 

 kind of pollen and work with large quantities, this difficulty might be over- 

 come by allowing the filter to become saturated with the extract. 



Table 18. Bacteria and Mold Colony Counts. Averages of Four Plates each. 

 1 : 100 and 1 : 10,000. 37°, 24 Hours. 



Dilutions 



Autoclaved 



