CEREAL IMPROVEMENT HYBRIDIZATION 217 



8 outside flowers of the 4 best spikelets about the middle 

 of each side of the spike, the middle flowers being emas- 

 culated but not pollinated. All other flowers on the spike 

 are either emasculated or removed. For a label, a small 

 white tag is tied to the culm, and the names of the par- 

 ents and date of the operation written upon it. An 

 average of about 60 per cent of flowers artificially cross- 

 pollinated set seed (Fig. 65). 



228. Limits of hybridization. Apparently varieties 

 of all the cultivated subspecies of cereals may be suc- 



FIG. "65. Cereal hybridizing nursery cage, for protecting the grain 

 from the ravages of birds. 



cessfully crossed artificially. Until recently the forms of 

 einkorn were never crossed with other subspecies, but 

 even this has now been done. Several successful crosses 

 have been made between wheat and rye, though very 

 rarely have these hybrids produced any seed. No such 

 crosses have succeeded, however, with rye as the female 

 parent. Leighty (1915) has described several cases of 

 natural wheat-rye hybrids. 



Oats and barley have not been crossed with rye or 



