ALFAXPA SEED PRODUCTION. 



29 



Table XX. — Pods and seeds formed on alfalfa plants at Pullman, Wash., in 1908 under 

 different conditions as regards shade and insect visitation. 





Conditions. 



Number 



of 

 flowers. 



Number 

 of pods 

 devel- 

 oped. 



Flowers 

 bearing 

 pods. 



Number of seeds. 



Plant. 



Total. 



Average 

 per pod. 





Flowers open to insects, sun, and wind.. . 



[shaded by one thickness of netting, in- 

 1 sects not excluded 



869 



207 



Per cent. 

 23.8 



574 



2.77 



No. 03 ... 

 NO.03-A. 

 No. 41... 



1 160 

 71 

 112 

 99 

 71 



35 

 21 

 31 

 22 



18 



21.8 

 29.5 

 27.6 

 22.2 

 25.3 



53 

 71 



88 

 43 

 41 



1.51 

 3.38 

 2.83 



No. 89.... 

 No. 89- A. 



Total 



1.95 

 2.27 





513 



127 





296 







Average 



24.7 



2.33 





■Entirely inclosed in mosquito netting 



Total 











No, 03... 

 NO.03-A. 

 No. 41... 

 No. 89... 

 No. 89- A. 



f 141 

 99 

 132 

 105 

 43 



14 

 7 

 4 

 2 

 



9.9 

 7.0 

 3.0 

 1.9 

 



19 

 19 

 5 

 3 

 



1.35 

 2.71 

 1.25 

 1.50 

 





520 



27 





46 







Average 



5.1 



1.70 















As shown in Table XX, 23.8 per cent of the flowers which de- 

 veloped under natural conditions produced pods. The average num- 

 ber of seeds per pod was 2.77. On the stems where the flowers were 

 screened from sun and wind by one thickness of mosquito netting but 

 which were open to the visits of honey-gathering insects, 24.7 per 

 cent of the flowers produced pods, which contained an average 

 number of 2.33 seeds each. On the stems which were entirely in- 

 closed by one thickness of mosquito netting, thus excluding insects, 

 5.1 per cent of the flowers produced pods, which contained an aver- 

 age number of 1.7 seeds each. 



In this experiment the proportion of flowers producing pods and 

 the number of seeds per pod were practically the same when the 

 flowers were screened from sun and wind by one thickness of mosquito 

 netting, which did not exclude insects, as when the flowers developed 

 under natural conditions. It is evident from these results that the 

 shade produced by a covering of one thickness of mosquito netting 

 had in this case no appreciable effect on the setting of pods. 



PRACTICAL ASPECTS OF TRIPPING. 



The recognition of the efflciency of tripping in the seed setting of 

 alfalfa makes it possible to secure inbred seed v/henever cross-polli- 

 nation is not desired. This can be accomphshed by isolating the 

 plants to any degree that is necessary and then tripping, using such 

 artificial means as are called for by the extensiveness of the opera- 

 tions. The observed increase of the seed crop thus obtained indicates 

 the possibihty of adopting this method on an extended scale to secure 

 alfaKa-seed crops, especially where the plants are grown in cultivated 



