Potato Breeding 79 



down on to the stigma. The flowers open in the morn- 

 ing and close late in the afternoon. Fruwirth says that 

 potato flowers usually give off pollen the second day 

 after opening and wilt the third or fourth day. The 

 period of flowering for a single plant is between 28 and 

 33 days. It seems to be a general opinion that the potato 

 flowers are only rarely visited by insects, and that wind, 

 also, plays little part in the pollination of the blossoms. 



The first thing to be done in hybridizing plants is to 

 decide on a definite ideal. We then choose our parent 

 plants with reference to this imaginary type, trying to 

 obtain plants which have as many as possible of the 

 qualities sought in the new form. 



Generally speaking, it makes no difference which 

 variety we use as male and which as female parent. A 

 great deal wiU depend on the nature of the varieties 

 themselves. Obviously, we must pick for male parent a 

 variety which bears at least a moderate amount of pollen. 



It is well to keep in mind a few general principles of 

 hybridization as we proceed. First, the plant to be 

 used as female parent should be emasculated to prevent 

 its setting seed by its own pollen. This must be done 

 before the anthers have matured. Secondly, it is safest to 

 bag flowers to be used in crosses, to prevent the entrance 

 of foreign poUen. And lastly, the pollen should be applied 

 to the stigma when that part is in a receptive condition. 



Mature potato flowers should be examined so that one 

 may become familiar with their structure. One should 

 learn when the anthers are mature and when the stigma 

 is ready for pollination. Just before the bud imfolds 

 the flower to be used as a seed parent is opened with a 

 pair of fine-pointed forceps. All the stamens are care- 

 fully removed, being careful not to break any or to leave 



