16 



BULLETIN 844, U. S. DEPARTMENT OF AGRICULTURE. 



This experiment was duplicated at Ames in August, 1916, with the 

 result that the three protected plants produced a total of 776 racemes, 

 with an average of 0.19 pod each. 



The plants inclosed at Arlington produced 0.44 pod to the raceme 

 more than the plants inclosed at Ames, and the average for the six 

 plants at Arlington and at Ames is only 0.42 pod to the raceme. 

 Results given below for nine plants inclosed in the glass-covered cage 



show that the pods 

 produced per raceme 

 by different plants 

 varied from 0.1 to 

 0.45, which is slightly 

 less than the varia- 

 tion in the two cages 

 covered with cheese- 

 cloth. 



In order to deter- 

 mine whether the 

 shading of the plants 

 in the cheesecloth- 

 covered cages had 

 caused the produc- 

 tion of seed to be re- 

 duced, a cage 4 feet 

 wide, 4 feet high, and 

 10 feet long, having 

 glass sides and top, 

 but with ends covered with cheesecloth to permit ventilation, was 

 placed over nine plants at Ames in August, 1916. The results 

 obtained in this experiment are presented in Table IV. 



Table IV. — Production of sweet-clover seed by plants protected from insect visitation 

 during their entire flowering period at Ames, Iowa, in 1916. 



Fig. 6. — Cage covered with cheesecloth to protect plants from insect 

 visitation. 



Plant. 



Racemes 



per 



plant. 



Pods pro- 

 duced 

 by all 



racemes. 



Average 

 number 

 of pods 

 to the 

 raceme. 



Plant. 



Racemes 



per 



plant. 



Pods pro- 

 duced 

 by all 



racemes. 



Average 

 number 

 of pods 

 to the 

 raceme. 



No.l 



84 

 130 

 166 



199 

 243 

 131 



17 

 58 

 30 

 88 

 35 

 36 



0.20 

 .44 

 .18 

 .44 

 .14 

 .27 



No. 7 



119 

 182 

 340 



13 

 S3 

 142 



0. 10 



No. 2 



No. 8.... 



.45 



No. 3 



No. 9 



.41 





Total 







1,594 



502 





No. 6 



.31 













The results given in Table IV show that an average of 0.31 of a 

 pod to the raceme was obtained from 1,594 racemes and that the 

 variation in seed production of the different plants was from 0.1 to 

 0.45 to the raceme. The average seed production for the nine plants 



