788 H. E. KnowitTon 
Antirrhinum pollen remains viable longest under conditions of low 
temperature (0° to —17° C.). The longevity decreased when pollen was 
stored in oxygen or at reduced atmospheric pressures. There is some 
evidence that high percentages of carbon dioxide in the atmosphere favor 
longevity. The maximum duration of germinative ability was 670 days, 
and of fertilizing power 161 days. 
The death of Antirrhinum pollen is not due to desiccation, exhaustion 
of stored food, or weakening of essential enzymes. 
Antirrhinum pollen is extraordinarily resistant to extremes of temper- 
ature, being able to withstand one as low as —180° C. and one as high 
asi o2y ©: 
Corn pollen is difficult to germinate. The optimum concentration for 
germination varied, depending on the conditions under which the plant 
had been grown. The best germination resulted in a 15-per-cent cane- 
sugar solution plus 0.7-per-cent agar. 
The moisture content of corn pollen was between 50 and 60 per cent, 
depending on the conditions under which the plants had been grown. 
The chief reserve carbohydrate in corn pollen is starch. Analyses 
showed that about 15 per cent, expressed in percentage of fresh substance, 
was present. 
Corn pollen remained viable longest under conditions of moderately 
low temperature (5° to 10° C.) and moderately high humidities (50 to 80 
per cent). This pollen was killed at a temperature of —17° C. The 
maximum duration of retention of fertilizing power was from seventy to 
eighty hours. 
Under normal conditions, the death of corn pollen is caused by desiccation. 
However, since life is not greatly prolonged by storage under conditions 
which retard evaporation, moisture is not the only important factor. 
Pollen may germinate in an artificial medium and yet be incapable 
of fertilizing a flower. 
ACKNOWLEDGMENTS 
The author acknowledges with pleasure kis indebtedness to Professors 
Lewis Knudson and O. F. Curtis, both of the Laboratory of Plant Physi- 
ology at Cornell University, for much valuable advice and criticism 
rendered thruout this work, and to R. 8S. Nanz, of the same laboratory, 
for his aid in collecting data. 
