1922] COFFMAN—POLLINATION IN ALFALFA 203 
This relation between dehisced anthers and flower length is shown 
graphically in fig. 5. 
From the data secured as the result of this preliminary investiga- 
tion, it appears that practically all alfalfa blossoms shed their 
pollen during the pointed bud stage, and before the hooded bud 
stage is reached. Judging by this, it would seem that tripping is 
not essential to pollination. 
The alfalfa flower apparently begins to shed its pollen while 
yet comparatively small, being only about 7 mm. in length, which 
in hybridization operations would necessitate emasculation being 
accomplished while the blossom is still in the straight bud stage, 
in order to eliminate all possible danger of self-fertilization. As a 
matter of fact, this is a practical impossibility from the mechanical 
standpoint in the field at least, the flowers being emasculated in 
alfalfa crossing work by tripping them not earlier than the hooded 
bud stage and generally later, the pollen then being washed out 
with an atomizer spray. It is impossible to emasculate the flowers 
earlier than the hooded bud stage. The writer believes, however, 
that there is great danger of pollination of the stigma and of con- 
sequent self-fertilization, before the time when the flowers are 
ordinarily tripped in alfalfa by hybridizing operations. 
This investigation was carried on in connection with graduate 
work under the direction of Professor H. F. RoBerts, of the Depart- 
ment of Botany, Kansas State Agricultural College. The illustra- 
tions are from pp. 202-203 of his paper referred to herein. 
U.S. DEPARTMENT OF AGRICULTURE 
Axron, CoLo. 
