288 POMOLOGY 



The work of Crandall,^ however, indicates that apple pol- 

 len may not remain viable so long as indicated by Sandsten. 

 After observations for three seasons, he shows that when 

 pollen was used that varied in age from one to eleven days, 

 "The percentages indicate no definite relation between age 

 of pollen and success obtained. . . . Apple pollen one month 

 old has been tested several times in drop cultures, but no 

 germination took place." He quotes Pfundt as finding that 

 the pollen of Pijrus Mains (presumably the wild apple of 

 Europe) retained its vitality in diy air for thirty-eight days 

 and when preserved over sulfuric acid, for seventy days. 

 "Records at the Illinois station contain no evidence of du- 

 ration of vitality beyond the fairly successful use of pollen 

 of Mains mains when eleven days old." Another investi- 

 gator reports that a few pollen-grains of apple germinated 

 after nearly three months and of pear after two months, 

 but no tests were made after longer periods than these.^ 

 Sweet cherry pollen also has a reasonably long period in 

 which it is viable, as germination tests showed it to be in as 

 good condition three weeks after it was gathered and dried 

 as when it was first collected.^ 



Further data show that pollen is not injured by a temper- 

 ature ranging from 25° to 55° C, if it be dry, but "at a tem- 

 perature of 40 to 50 degrees C, in a saturated atmosphere, 

 the pollen grains burst open due to the rapid inhibition of 

 water and the number of bursted pollen grains increased as the 

 temperature increased. Freezing temperatures ranging from 

 — 1.5 to — 1 degree C. were not seriously injurious to the pol- 

 len of apple, pear, and plum while less than 50 per cent of 



iCrandall, C. S. The vitality of pollen. Soc. Hort. Sci. 1912. 

 pp. 121-130. 



2 Adams, J. Germination of the pollen grains of apple and other 

 fruit trees. Bot. Gaz. 61:131-147. 1916. 



3 Ore. Agr. Exp. Sta. Bull. 116. 1913. 



