A NOTE ON THE DROPPING OF 



FLOWERS IN THE POTATO* 



M. J. DORSEY 



Head of the Section of Fruit Breeding, Agricidtural Experiment Station of the 



University of Minnesota 



THERE is considerable popular 

 interest in the failure of many 

 potato varieties grown today to 

 set seed. The varieties of our 

 forefathers are generally supposed to 

 have set seed-balls in abundance. It 

 has been generally held that the cooler 

 northern States such as Minnesota fur- 

 nish conditions favorable to the devel- 

 opment of seed-balls, but recently 

 Newman and Leonian report seed-ball 

 production in the Lookout Mountain 

 variety (when grown as far south as 

 Georgia) that certainly equals seed pro- 

 duction farther north at its best. In 

 fact these investigators are attempting 

 to develop varieties which will produce 

 by seed as well as by tubers. An occa- 

 sional year when seed-balls are more 

 abundant than others is well known, but 

 the interest of growers centers more 

 around those years when the flowers 

 are abundant, but seed-balls rare, if any 

 develop. The disposition of the flowers 

 in the last case is the theme of this 

 article. 



It should be stated that flower pro- 

 duction varies from year to year and 

 also that some varieties habitually bear 

 fewer flowers than others. For in- 

 stance, King seldom produces flowers, 

 while Green Mountain bears them in 

 abundance. It follows then that seed- 

 ball production must also vary from 

 year to year and between varieties. 

 Some contend that seedlings bear more 

 seed-balls than the older varieties. 



Early Ohio (Fig. 19, Nos. 1 and 2) 

 and Rural New Yorker bore flowers in 

 abundance at the Fruit Breeding Farm 

 in 1918; but, like so many other seas- 



ons, all fell off so that at harvest time 

 not a single seed-ball could be found in 

 the entire patch. What happened? 

 An examination of the blossoms when 

 the flrst flowers were open showed 

 that both the opened flowers and buds 

 were falling in large numbers. In some 

 clusters there was a partial succession 

 of bloom, but the first flowers to open 

 fell as the later ones came into bloom. 

 In others the younger as well as older 

 buds were falling several days in ad- 

 vance of the time they were due to open. 

 In still others the younger buds fell 

 before those which had come into full 

 bloom. It is unusual to flnd dropping 

 taking place simultaneously in flowers 

 differing so much in age, because in most 

 cases flowers normally fall after ma- 

 turity. 



The joint in the pedicel (Fig. 19, No. 

 1) at which the flowers drop is three to 

 five millimeters below the flower. There 

 is a conspicuous swelling in the pedicel 

 at this point, and before the flowers fall 

 the stem is noticeably yellow in the 

 younger buds as well as those which 

 have opened. Buds or flowers some- 

 times drop on clusters in which seed-balls 

 have already developed, and rarely even 

 the younger seed-balls may drop. There 

 is no abscission layer subtending the 

 flower stalk, and after the flowers have 

 all fallen off it persists and, in the ab- 

 sence of leaves at the base, dries up 

 and can be found in this condition at 

 maturity. 



In many of the varieties a large per- 

 centage of the pollen is defective and in 

 some no normal pollen is produced 

 (Fig. 19, Nos. 5 and 7). Counts in a 



1 Published with the approval of the Director, as Paper 161 of the Journal Series of the 

 Minnesota Experiment Station. 



226 



