ALFALFA 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. 








NeeaD Number of seeds. 
Number | * haa ae Flowers 
Plant. Conditions. of “level. | bearing 
flowers. oped. pods. Total. ae 
Per cent. 
Flowers open to insects, sun, and wind... 869 207 23.8 574 PI UU 
No. 03 . Geo 35 21.8 53 1.51 
No. 03-A. Shaded by one thickness of netting, in- a a aa ge sols 
NO “if sects not excluded a5 a ale . ie 2. 83 
(0) oll] [ae ea oa Se Ra ee = : 1.95 
No. 89-A. 71 18 25.3 41 2F 27; 
LNG a in a Sg ST 513 DPA fee) ae ea aa 296) | 2 vee semen 
INSTR Sa SHOR OS son es UN ox ay a eget) (NL hs se I a ee DAN T| eR ete 2.33 
No. 03 ... 141 14 9.9 19 1.35 
No.03-A. aes ‘ 99 7 7.0 19 vi 
No. 41 ...|$Entirely inclosed in mosquito netting. ... 132 4 3.0 5 1.25 
No. 89... 105 2 1.9 3 1.50 
No.89-A. 43 0 0 0 0 
AINE RS co ae rs I IN ES eee 520 Diller ees olive oid em aenre ee 

Average.......---. lek mul SPA A LD | grea Heli | EW d i Aaga ogee 1.70 
As shown in Table XX, 23.8 per cent of the flowers which de- 
veloped under natural cont Hime 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 efficiency of tripping in the seed setting of 
alfalfa makes it possible to secure inbred seed whenever cross-polli- 
nation is not desired. This can be accomplished 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 possibility of adopting this method on an extended scale to secure 
alfalfa-seed crops, especially where the plants are grown in cultivated 
