348 GENETICS IN RELATION TO AGRICULTURE 



but a number of natural hybrids in wheat have been reported, especially 

 in sub-tropical countries. In the immature flower the anthers are short 

 and closely packed around the pistil. Just before anthesis the filaments 

 lengthen sufficiently to allow the anthers to protrude when the flower 

 opens. Castration can be accomplished without difficulty by choosing 

 flowers nearly ready to open and removing the later flowers on the upper 

 portion of the spike as shown in Fig. 143, lower right. With a pair of 

 fine forceps the lemma and palea are forced apart and the anthers care- 

 fully removed. From a head of the desired male parent anthers just 

 ready to burst are then removed and an anther is placed in each of the 

 castrated flowers (Fig. 144). Two pairs of forceps should be used, one 



FIG. 145. Sexual columns of alfalfa flowers (enlarged 7 diameters), showing differ- 

 ent stages of development: A and B, anthers just before dehiscence: C and D, anthers 

 dehisced;!? and F, after treatment with water jet previous to artificial pollination. 

 (After Oliver.} 



for castrating and the other for pollinating; or, if the same instrument is 

 used, it should be sterilized by dipping in alcohol between each operation. 

 After pollination the spike is bagged or wrapped with several thicknesses 

 of cheesecloth and labeled with a paper string tag. The use of the cloth 

 and light weight tag is to be preferred because most grain plants will 

 support this extra weight without staking (see Fig. 144). 



A Method of Hybridizing Alfalfa. An ingenious method of crossing 

 this and similar small flowered species has been worked out by Oliver. 

 The essential points are as follows: First, have. pollen from male parent 

 at hand ready to be applied to the prepared stigmas. This is accom- 

 plished by taking a flower from a raceme of the male parent, securing the 

 banner between the thumb and forefinger and pressing a pin against the 

 suture of the keel, beginning at the base and gradually drawing it upward. 

 When this is done carefully the stamens and pistil come out gently 

 without disturbing the masses of slightly adhesive pollen (see Fig. 145, C, 

 D). Now with the aid of self-closing forceps sever the sexual organs from 



