C2 H. E. KNOwLTon 
Mangin (1886). If the temperature remains low, Antirrhinum pollen 
should remain viable for five months or longer, tho the variability of 
pollen may necessitate a qualification of this statement. 
Possible causes of death of Antirrhinum pollen 
Loss of moisture 
As Antirrhinum pollen has a low water content, it was believed that 
moisture conditions would not affect longevity to any great extent. Under 
very humid conditions, however, moisture collected on the pollen and 
contaminations by molds soon resulted. 
To determine whether the Antirrhinum pollen would lose moisture 
rapidly, a small quantity of pollen was spread on a watch glass, weighed, 
and placed in the incubator at 25° C., where the humidity ranged from 
20 to 40 per cent. Weighings were made daily. At the end of seventy 
days the weight was practically the same as at the beginning. Slight 
fluctuations occurred during this period, as the humidity within the 
chamber varied. Since little moisture loss occurred, this sample of 
Antirrhinum pollen must have been in equilibrium with the atmosphere 
at this particular humidity. The fact that the pollen had lost little 
water, altho exposed for seventy days to an atmosphere low in humidity, 
would indicate that moisture loss does not condition the duration of 
viability. 
Respiration experiment - : 
Exhaustion of the stored carbohydrates suggested itself as a cause 
of death. Since the water content is low, metabolic processes, and 
particularly respiration, should be less active. To determine the truth 
of this, an attempt was made to study respiration. Several methods were 
tried, but none were successful because the amount of carbon dioxide 
given off was so very small. Difficulties were enhanced by the neces- 
sarily small amounts of material. The conclusion drawn from these 
attempts was that the respiration rate of Antirrhinum pollen is very 
low — probably comparable to that of seeds having a low moisture content. 
Depletion of cane sugar 
Altho respiration seemed a negligible factor, it was deemed advisable 
to make carbohydrate analyses of fresh and stored pollen,’ in order to 
