ALFALFA SEED PRODUCTION. 95 
TaBLE XV.— The setting of alfalfa pods by flowers when the standard was removed and 
the keel severed at base. 
| Number of seeds. 
Num- | Number | Number | Flowers 
Observer. Place. Year. | ber of |offlowers| of pods | bearing 
plants. | tripped. | formed. | pods. Total, | verage 
* | per pod. 
Per cent. 
Westgate......- Washington, D.C.| 1908 13 246 52 QUE is Ue 4 |e aaa ane 
Morse.......... Arlington farm....| 1908 10 120 19 15.9 28 1.4 
1 BX oy ease | (RNC oe Goze eae 1909 1 6 22 12 54.0 23 1.9 
AD Yo yest ee ata a a GORE yaa ae 1909 2 8 27 11 40.8 19 1.7 
Evans.........- Pullman Washi. | 71909 ts2 5.25. 76 13 LU erat etsc ictal ercleteetareteete 
1 Plants screened. 2Plants not screened. 
The proportion of pods to flowers is in fair agreement with those 
tripped otherwise. It would seem, therefore, that no importance can 
be attached to the keel as a passive agent of friction when the column 
retracts. : 
ARTIFICIAL AGENCIES EFFECTIVE IN TRIPPING. 
Any force giving sufficient pressure on the keel, either laterally or 
vertically, will result in tripping the flower. This may be accom- 
plished by means of the fingers or even by the hand in grasping an 
entire cluster or bunch of clusters. Tripping may also be accom- 
plished by means of a stick, straw, or pencil point inserted into the 
flower and then separating the posterior processes of the wing petals. 
In order to determine the relative effect of these various means, an 
experiment was carried out in which tripping was accomplished in 
the following ways: (1) Each flower tripped with a small piece of 
- wood, (2) with a pencil point, and (3) rolled between the fingers. 
The data obtained (Table XVI) show little difference in the effects 
produced by these various methods of tripping. 
TaBLE XVI.—-Effect of tripping alfalfa flowers by different mechanical methods, at 
Arlington farm, Virginia. 
Number of seeds. 
Number Naber Flowers 
Method of tripping. | Year. Plant. of pods. 
(0) 
flowers. 
pods. Average 
Total. per pod. 
Per cent. 
With a small piece of |f 1908 | F.C. I. No. 18....... 21 3 14.2 7 2.3 
wood. | 1909 | F. 6 i nee MS 12 4 33 : 3 ie 
A 2 Z 1908 EF, . No. 18 76 18 ils 
With a pencil point..\) i999 | F1G.1.No.1........ 42 22 52.3 38 1.7 
, 1908 HS CHINO nel Siese a: 75 40 5 Se 
Byroling perncey the!} 1993 | F.C. 1, No.1 22 7 31.8 9 1.3 
Ee eS Pq OOO). |< (5 (a aN Na Ue 43 21 48.8 42 2.0 


