144 Cross-Fertilisation in Potatoes. [may, 



this case it is advisable to employ an abundance of pollen and 

 then replace the bag and leave it for several days. 



Some investigators will require to self-fertilise rather than to 

 cross their plants. In this case the procedure is simplified. 

 It is only necessary to remove all open flowers from the cyme 

 and to protect the unopened buds (without further operation) 

 by the bag, affixing the label as before. \Mien the flowers are 

 opened an anther should be removed and the pollen distributed 

 on the stigma in the same manner as was done when cross - 

 fertilising. The bag should then be replaced. It is important 

 to remember that the sterility of an anther, so common in 

 potatoes, is a dominant Mendelian character, and unless this 

 is recognised difficulties will arise in later generations.* 



Raisers should not be disappointed if they find the number of 

 successful fertilisations to be small. Over a large number of 

 years and using a great variety cf plants, the number of success- 

 ful fertilisations was never more than 5 per cent, of individual 

 flowers treated, or, allowing three flowers to each pollination, 

 15 per cent, of the total number of female parents. 



* For information on this subject the investigator is referred to the following 

 papers : — * 



" The Inheritance of Colour and Other Characters in the Potato," Journal 



oj Genetics, Vol. i, No. i, Nov., 1910. 

 " Male Sterility in Potatoes," The Journal of the Linnean Society, Botany, 

 Vol. xxix., October. 1910. 



