406 IOWA ACADEiMY OF SCIENCE Vol. XXV, 1918 



included in the investigation. In apple pollen, we found abund- 

 ance of starch present in the early bud stage but none at the 

 time of pollination. 



Sandsten (19) and Adams (1) have investigated the germi- 

 nation of apple pollen, both using sugar solutions, but neither 

 determined the function of the sugar in the solutions or investi- 

 gated the stigma in relation to the germination of the pollen. Of 

 the five varieties included in our work, Sandsten included the 

 Duchess. We found 2i/2 per cent cane sugar solution most fa- 

 vorable for germination, which is closely in. accord with their re- 

 sults, Sandsten using 3 per cent and Adams 5 per cent solutions. 

 In our work the sugar was found to aid only in controlling the 

 water supply. Better germination was secured on membranes 

 soaked in distilled water and then dried until surface moisture 

 was removed. Examinations of stigmas under ordinaiy condi- 

 tions of pollination showed no liquids on the surface ami that 

 the situation of the pollen on the stigma is similar to that on 

 the membrane. 



The temperature found in our work to be the most favorable 

 for germination was in accord wdth the observations of Sand- 

 sten and Adams. Schaffnit (20) and Chandler (3) exposed ap- 

 ple pollen to temperatures of — 17° C. and — ^18° C. for long peri- 

 ods when the pollen was dry without any. apparent injury. 

 Sandsten (19) found that an exposure of apple pollen to a tem- 

 perature of — 1.5° for less than one hour resulted in very little 

 injuiy. He exposed the pollen on dry watch glasses. Chandler 

 (3) does not state how the pollen was exposed which he consid- 

 ered not dried and found not injured by a temperature of — 8° 

 C. We found that pollen could be frozen up solid in water and 

 sugar solutions without being injured. 



Sandsten found the stigmas more susceptible to cold than the 

 pollen. They were killed when exposed a few hours to a tempera- 

 ture of — 1.5° C. He does not state tow the injury was indicated. 

 We found that the stigma at the time of pollination is appar- 

 ently dead under ordinary conditions, but that temperatures a 

 little below freezing kill the style. We also found that pollen 

 germinated on a stigma which has been exposed to a temperature 

 low enough to kill the style. 



The length of time which pollen can remain viable in storage 

 depends very much upon storage conditions. Lidfors (9, 10) 

 and Pfundt (17) have shown that pollen kept uniformly dry 



