HYBRIDS 133 



prefers the pollen of our butternut to its own pollen 

 at times. A number of instances have now been 

 recorded in which the progeny from nuts of the 

 Japanese walnut gave butternut hybrids, although 

 both trees were blossoming at the same time. 



One way for retarding the development of male 

 flowers until they are wanted for pollinizing pur- 

 poses consists in cutting branches carrying immature 

 catkins and putting them in cold storage. I have 

 retarded the development of hazel flowers for a fort- 

 night by placing them beneath the sawdust near the 

 ice in the ice house when wishing to use American 

 hazel pollen for European or Asiatic species, which 

 blossomed considerably later. When the time comes 

 for allowing male catkins to develop, the branches 

 are placed in jars of water in a sunny room with 

 closed windows. These blossoms will shed pollen in 

 a few days. 



The plant breeder cannot always be sure that he 

 has made good hybrids when nuts develop upon 

 branches, the female flowers of which have been 

 artificially pollinized. Apparently the pollen grain 

 excites some cell of the female flower into develop- 

 ment at times without making fusion. In that case 

 we get a parthenogen, a plant with but one parent, 

 the mother. 



Only a small proportion of hybrids present char- 

 acteristics which are particularly valuable. When 

 the chestnut blight appeared in Connecticut I set out 

 with the idea of finding kinds of chestnuts which 

 would resist the blight and got together from dif- 



