ALFALFA SEED PRODUCTION. 31 



GENERAL CONCLUSIONS. 



The numerous researches of previous investigators on the pollina- 

 tion of the alfalfa flower have resulted in somewhat divergent con- 

 clusions. In but few cases has any attempt been made to determine 

 the relation of pollination to the resultant crop of seed. 



The opinion has prevailed that insect pollinizers are of vital im- 

 portance and that in the absence of these in adequate numbers the 

 resultant seed crop is necessarily small. 



It has, however, been generally recognized that cUmatic conditions 

 are important, as practically all the commercial seed is raised in 

 regions having a semiarid climate, at least during the time the seed 

 crop is made. 



Alfalfa flowers remain fully susceptible to poUination from the time 

 of opening until the petals wither. PoUination is ordinarily effected 

 when the elastic stamineal colimm has become "tripped." No 

 evidence was found to favor BurkiU's theory that tripping effects 

 the rupture of the stigmatic ceUs and that this is an important factor 

 in fertihzation. Flowers tripped in various ways to prevent any 

 stimulation or rupturing of the stigma by contact set pods equally as 

 well as those tripped naturally. 



Flowers tripped artificially, and therefore self-poUinated, set pods 

 freely. In one series of experiments on 77 plants at 7 different places, 

 9,074 flowers set 2,784 pods when artificially tripped (a percentage 

 of 30.68), while 8,939 flowers on the same plants exposed to natural 

 conditions set 1,499 pods (16.76 per cent). The pods from artifi- 

 cially tripped flowers contained an average of 1.72 seeds each, while 

 those from naturally tripped flowers averaged 2.22 seeds each. 



PoUination from a different flower on the same plant is no more 

 effective than seK-poUination, but poUen from another plant increases 

 both the proportion of pods set and the number of seeds per pod. It 

 makes but Httle difference whether the poUen parent be the same or a 

 different variety. 



Tripping in alfalfa flowers may be automatic or may be effected by 

 insects and other external agents. Untripped flowers form pods and 

 seeds only in rare instances. Automatic tripping is a normal phe- 

 nomenon. On two plants at Chinook, Mont., in 1909, 33 out of 57 

 marked flowers became automatically tripped on one plant and set 

 21 pods, and under the same conditions 64 flowers on the second plant 

 produced 16 pods from 36 automaticaUy tripped flowers. The per- 

 centage of pods to flowers on the first plant is 36.84 and on the second 

 25. These are quite as high as normally occur under natural field 

 conditions. In a simUar experiment at Pullman, Wash., in 1910, 60 

 flowers out of 775 on 9 plants became seff- tripped, and 21 of these 

 set pods. In this case only 7.74 per cent of the flowers automati- 



