STuDIES IN POLLEN, WITH SPECIAL REFERENCE TO LONGEVITY 765 
Duration of receptivity of the stigmas of Antirrhinum 
In any pollination experiment, data concerning the duration of stigma 
receptivity are important. Few investigators of pollination problems 
study this phase of the work, however. As has been mentioned, Dorsey 
(1919) determined this period for the plum, and Anthony and Harlan 
(1920) for barley. 
In order to find out the length of time stigmas of Antirrhinum remain 
receptive, the following experiment was conducted. A. large number 
of flowers were emasculated prior to the time the petals unfolded, and 
pollinations with fresh pollen were made at intervals up to several weeks 
after the opening period of the flowers. Results of this experiment are 
given in table 6: 
TABLE 6. Duration oF RecEptivity oF ANTIRRHINUM STIGMAS 
Ny = Number 
Day after flowers opened Niviaeloay | Nubecioe: not 
pollinated | fertilized | ) fertilj 
ertilized 
SL SUITL ORC hy MMM IR Arora siednSahs Sieganciahejso a gah ainaue Wa aR 11 9 2 
HEM,» 5 0.6 5.610 6 0.6 © 6/6 a eR IOONEN ae RE RPIEET Epa Netra ae ae 6 6 0) 
DUDs 6 0 8 6 66 0.0 & Bio dia! chen aT REC ea ORE RENaIN eNE eon aeniSnet ne 6 6 0 
Giles ooo b.6'4 Sule ad's Sa ae a ae Ta arene RI 8 8 0) 
IQ. :5 a5'5.0°0 o's GBs CERES a eRe ec ae ee 11 10 1 
IA CPR rte el ee Ol ee ye UA anhctl glare Gey br 7 1 6 
HG PPI ere a Lotus ance taadarpaieee Makes ote 5 3 2 
IS Geena tna ec uu ithe Lecideadtaes ak 4 0 4 
PASS oo 6 5 6-0 oho od Sc ME EI ene ie perenne eat 11 2 9 
ZRBC oc c06bdy 5 ORO A ae eee Pant LOE. foet aiat st ag) By ior 0 5 
DRT 5 6 0 cle se 6 6 5002s ee a . 5 0 | 5 
Two weeks after pollination, capsules were produced, but these were 
smaller and contained a smaller number of seeds. The pistils of emas- 
culated flowers, if the pollen was withheld for any length of time, grew 
to an abnormal size. After from fifteen to eighteen days, the pistils 
began to wither. 
These results show that after ten days the percentage of fertilization 
decreased, altho several fertilizations took place on flowers three weeks old. 
The duration of receptivity of corn stigmas was not determined. It is 
generally understood by plant breeders, however, that corn can be polli- 
_nated successfully until the silks begin to wither. 
