STUDIES IN POLLEN, WITH SPECIAL REFERENCE TO LONGEVITY, 781 
TABLE 27. Corn Pouten in Dessicator at 25° C. ano 35 Per Cent Humipity 
Ears ora. A Water 
Age molnated Fertilization ast 
Hours Number Per cent Per cent 
(mre Dia ey Ud 1 70 1 
Dy 5.5.0 056°6 ca Ba O44 Oo ee ae 1 60 12 
Do o1:0 06.8 ois OS ore ee eae ao ae eS 2 36-55 26 
el NMED ee ea aS ee ec ordre d dlarwdia eels ay la 1 30 43 
DB ao 0 6.0.0 6 Ole iO. Gi Ge ERE ae ae ea ore 1 1 74 
However, pollen remains viable after considerable desiccation. Thus, 
table 26 shows that fertilization took place even when 88 per cent of the 
water content had disappeared. In these experiments, the pollen was 
spread out on the watch glasses in as thin layers as possible, in an attempt 
to get the same amount of evaporation from each grain. It is probable . 
that the few successful pollinations, after twelve and twenty-three hours, 
respectively, were due to pollen grains so favorably situated as to hold 
a larger amount of water. However, the results show that grains may 
lose from 40 to 50 per cent of their water without materially impairing 
their viability. 
Experiments on respiration 
In addition to desiccation, other factors which might impair viability 
suggested themselves. Since the moisture content of corn pollen is high, 
respiratory activity would probably be great. As a result, exhaustion 
of stored food might occur, and this would probably be accompanied by 
protoplasmic changes. 
Respiration was first determined. Due to the small amounts of material 
available, difficulty was experienced in finding a method by which such 
small amounts of carbon dioxide could be accurately measured. Truog’s 
(1915) method, as modified by Gurjar (1917), was finally used. This 
method consists essentially in catching carbon dioxide in a special form of 
absorption tower, containing standard strength of barium hydroxide, 
and titrating the remaining alkali against a standard acid. The results 
are given in table 28. 
Ag was expected, the respiratory activity was high, diminishing rapidly 
in a dry atmosphere. However, it was not rapid enough to exhaust 
