26 



BULLETIN 75, U. S. DEPAETMENT OF AGRICULTURE. 



EFFECT OF AGE OF FLOWERS UPON SUSCEPTIBILITY TO FERTILIZATION. 



An expeiiment by Westgate vras performed in one of the green- 

 houses of the United States Department of Agriculture at Washing- 

 ton, D. C, for the purpose of determinmg whether the age of the 

 flower affects its susceptibility to fertiUzation. A single plant of 

 Peruvian alfalfa (F, C. I. No. 60) was used in this experiment. A 

 number of young, prime, and old flowers were artificially tripped. 

 For the purpose of comparison, a number of flowers at each stage of 

 development were marked, but not tripped. Table XVII shows the 

 percentage of flowers which produced pods under each method of 

 treatment. 



Table XVII. — Pod setting in relation to age of alfalfa fiou-ers when tripped. 



Age. 



Number 

 of flowers 

 tripped. 



Number 

 of pods 

 formed. 



Flowers 



bearing 



pods. 



Flowers 



not 

 tripped. 



Number 

 of pods 

 formed. 



Flowers 



bearing 



pods. 



Young flowers 



15 

 34 



81 



7 

 17 

 40 



Per cent. 

 46.66 

 50.00 

 49.38 



18 

 38 

 89 





 

 3 



Per cent. 

 



Pn'mp flowprq 







Old flowers 



3.37 







A similar experiment, designed to show at what stages of its devel- 

 opment an aKalfa flower may become fertihzed and also to throw 

 some light on the question as to how long it may remain capable of 

 fertilization, was conducted -at Pullman, Wash., by Evans m 1909. 

 All opened and wilted flowers were removed from a number of 

 racemes on five different plants inclosed in netting tents. On the 

 following day all unopened buds on these racemes were removed, leav- 

 ing only those flowers wliich had opened during the preceding 30 hours. 

 As the experiment was carried out in September, when the weather 

 was comparatively cool, the flowers remained fresh and open for a 

 longer period than would have been the case in warmer weather. A 

 number of the flowers on these racemes were tripped each day up to 

 the end of seven days, when the tips of some of the petals were begin- 

 ning to ^vilt. The experiment was discontinued at this time because 

 the suppl}' of flowers was exhausted. The number of the flowers 

 that were tripped and the percentage of tripped flowers which pro- 

 duced pods are shown in Table XVIII. 



Table XVIII. — Results obtained at Pullman, Wash., in tripping alfalfa flowers at 

 different intervals after blooming. 



Time from opening of flower until tripped. 



Number of 

 flowers. 



Number of 



pods 



formed. 



Flowers 



bearing 



pods. 



1 day. 



2 days 



3 days 



4 days 



5 days 



6 days 



7 days 



Per cent. 

 27.18 

 26.08 

 87.50 

 82. 81 

 24.05 

 62.83 

 25.00 



