260 



SCIENTIFIC AGRICULTUKE. 



April, 1922. 



carefully upwards to the top. After the 

 slit has been made, the pistil will spring 

 back very slightly, Ijringing the stigma 

 away from the face of the standard ; thus 

 showing that it has been pushed into posi- 

 tion and held there by the force exerted 

 by the staminal tube in which it was 

 inclosed. 



Methods of Emasculation. 



In hybridization experiments, the me- 

 thod of emasculation generally practiced 

 is that of selecting a flower in the bud 

 stage, carefully removing the immature 

 anthers before they have lost any pollen; 

 then, when the stigma has assumed a 

 moist, receptive condition, transferring 

 suitable pollen to the stigma; finally, in- 

 closing the flower in a paper bag or muslin 

 bag until fertilization has taken place. 



This method was tested on a large num- 

 ber of flowers, the work being done under 

 varied w^eather conditions and at various 

 periods of the day — morning, evening, and 

 midday; but the results were far from 

 satisfactory. Very few of the floAvers 

 that were operated upon produced seed. 

 This want of success is, perhaps, not very 

 surprising when all is eonsidered. 



An Alfalfa flower in the bud stage is 

 very small and not easy to handle. It is 

 also very soft and delicate and difficult 

 to emasculate without causing such mutila- 

 tion of the flower as will prevent fertiliza- 

 tion taking place. Again at this stage of 

 development, the stigma not being in a 

 condition to receive the pollen, it is neces- 

 sary to wait from one to two days after 

 emasculation before pollination should be 

 attempted. This means further handling 

 of the flower and risk of further bruising 

 or mutilation. 



The second method of emasculation 

 A\'hich was tested is the one originated and 

 recommended by George W. Oliver of the 

 United States Department of Agriculture, 

 Washington, D. C. (2). The main princi- 

 ples of this S3'stem have been followed in 

 the present investigations with some 

 slight modifications in details. The mo- 

 dified method may briefly be described 

 as follows: — 



The flower selected to be operated upon 

 should be fully open but quite fresh and 



in a healthy vigorous condition and not 

 tripped. The operation consists in first 

 tripping the flower so as to expose the 

 sexual organs; then carefully removing 

 the i)ollen, after which the stigma may at 

 once be pollinated. 



It has already been explained that 

 during natural tripping of the flower, the 

 sexual column is released from the keel, 

 and the bursting anthers, together with 

 the stigma, are forced against the face of 

 the standard ; thus ensuring self-pollina- 

 tion. Bearing this in mind, it is quite 

 obvious that if we wish to practice cross- 

 pollination, self-pollination must be pre- 

 vented. This may be brought about in the 

 following manner : — In tripping the flow- 

 er, the operator, using a small toothpick, 

 presses lightly on the upper surface of the 

 keel at a point near the base : this pres- 

 sure is sufficient to release the keel 

 petals; thus to allow tripping to take 

 place. 



In performing this operation of trip- 

 ping, it is necessary to insert some object 

 between the sexual column and standard, 

 which will effectually prevent the an- 

 thers and stigma from coming in contact 

 with the standard. After testing various 

 articles for this purpose, it was found 

 that the flowering stems of well-ripen- 

 ed Timothy cut into suitable lengths of 

 about one inch served the purpose ad- 

 mirably. By taking one of these stems 

 and using a firm, gentle pressure at the 

 base of the keel, the sexual column is 

 caused to trip gradually against the piece 

 of Timothy stem: this light object is easily 

 held in a position just beloAv the anthers 

 and stigma; and it is sufficiently strong 

 to prevent the anthers and stigma from 

 coming in contact with the standard (fig. 

 II B; fig III B.) 



By means of a pocket lens, it may now 

 be observed that tlie anthers are close- 

 ly packed around the stigma. Some may 

 have burst and the stigma may be covered 

 with pollen. The next operation is to 

 remove the anthers and free pollen: this 

 may be done by bringing a very fine jet 

 of water to play upon the surface of the 

 stigma and surroimding anthers and, by 

 this means, both loose pollen grains and 

 anthers are carried away very effectually. 

 "For this purpose a small hand-sprayer 

 with rubber bulb and fine nozzle has been 



