780 H. E. KNow.tTon 
humidity. Altho the results of corn-pollen storages are not conclusive, 
it is justifiable to say that fairly low temperatures- (5°-10° C.) are more 
favorable than high temperatures or temperatures below freezing. Pollen 
lives longer at moderately high humidities (50-70 per cent) than in a dry 
atmosphere. However, if the humidity is too high, the pollen becomes 
sticky. Under the optimum conditions, as stated above, good, virile corn 
pollen should live for three days. The results show that pollen varies 
greatly in different seasons, however. 
Possible causes of death of corn pollen 
Loss of moisture 
Andronescu (1915) found that corn pollen lost moisture rapidly when 
exposed in the open air or in a desiccator. He concluded that death 
was caused by this drying out. The following experiments were per- 
formed to gather additional data. Several grams of fresh corn pollen 
were spread out evenly on a large watch glass and carefully weighed. The 
watch glass was then placed in a desiccator and weighings were made as 
shown in tables 26 and 27. From a similar, but unweighed, sample, 
adjacent to it, pollinations were made at the same time that the weights 
were taken. 
In a dry atmosphere, corn pollen loses moisture rapidly. Some of 
this loss in weight is obviously due to the carbon dioxide given off in 
respiration, but the calculated correction for this loss is only 6 per cent 
for the figures given in table 26, and 9 per cent for tlie values in table 27. 
TABLE 26. Potten in Destccator over Caucrum Cunoripe at 25° C. 
; Ears Sy Apia no Water 
Age polliveted Fertilization last 
Hours Number Per cent Per cent 
OR ae eee Rae Us musin cet wee Rasen gn! sn MOR 2 75 0 
DA MGV aHOEAT AVS U Ny Re SINR nt Weiibweed Nel See gn, ate ht A ee peat 1 60 14 
ANEOCN nian bane e(“aEU ere LR LW. AS cau agee eat k 1 80 26 
GRAS CRI Aisne Men epee DIA kena Rd (eda un if 70 37 
pear tee a) rN eared dean Teast CUM ARE ap laln Mee le ey 2 40-60 48 
TIC es at maT BN OR SMO CSLLANE SUSU ies CSOT SR eet a 2 5-65 58 
Ue iden 5 PILAR cE REA ie SNe Co POU SR 2 1-20 79 
DOE OES ADM Leia ULI ammE Me MeL Loa Me TnI MAM hh! 8 2 0-10 94. 
