STUDIES IN POLLEN, WITH SPECIAL REFERENCE TO LONGEVITY 759 
decreases with age. Crocker and Groves (1915) advance a theory that 
the loss of viability of seeds in storage is due to a slow coagulation of the 
proteins in the plasma of the embryo. They applied Buglia’s (1909) 
time-temperature formula for protein coagulation and found it applicable 
for a temperature-life-duration formula for seeds. This formula is 
T =(a-b) log Z 
in which T represents the temperature and Z the time of heating, and a 
and 6 are constants. Several factors, such as the increase in acidity of 
the seed, the redispersal of proteins in seeds of high water content, and 
variability in the water content, may limit the general application of this 
formula. A slight error in a and b gives a relatively large error for a life 
duration at low temperatures. - 
There are no records of attempts to determine whether the death of 
pollen is due to any of these causes, that is, exhaustion of stored food, 
destruction of enzymes, or coagulation of proteins. 
EXPERIMENTAL WORK 
Description of pollen 
Pollen of snapdragon (Antirrhinum majus L.) 
The pollen of snapdragon is produced very abundantly. It is yellow 
in color and is covered with a gummy substance which causes the grains 
to adhere to one another. As this sticky pollen cannot be wind-carried, 
cross-pollination is effected by bees and other insects. The pollen is 
rather below the average in size; is oval in shape, when dry, but when 
turgid, in a sugar solution, is nearly spherical. Dry pollen measures 
26.5u in length, and 15.34 in width; when turgid, the average diameter 
is 24u. Halsted (1889) has noted a similar change in shape with other 
species of pollen. When dry, the position of the germ pores is marked 
by three long folds in the wall. These folds are less distinct when the 
cell becomes turgid. 
Analyses of fresh pollen show that cane sugar is the reserve carbohy- 
drate, the amcunt present, expressed in percentage of fresh substance, 
varying from 8 to 10 per cent. Small amounts of reducing sugars are 
also present, but no starch was detected. 
Other investigators have made chemical analyses of pollen. Van 
Tieghem (1869) observed that some species of pollen store cane sugar. 
