140 



Cross-Fertilisation in Potatoes. 



[may, 



open should be nipped off with the forceps, leaving from three 

 to five buds. These buds should, as far as possible, be all of 

 the same size, about J in. in length and in such a stage as to be 

 ready to open. Buds which are considerably younger than 

 this should be removed. The operator then dips his forceps 

 into the bottle of alcohol for one or two seconds, shakes them 

 to allow them to dry, then takes the bud between the finger 

 and thumb of his left hand and very gently pushes open the 

 petals. He will then find the anthers closely clustered round 

 the stigma, and on inserting the fine point of his forceps very 

 carefully between any two on the anthers and pushing the 

 anthers outwards, he will fmd that they break off and are 

 readily removed. All five anthers must be similarly treated 

 and every bud of the group must be likewise emasculated. 

 With very little practice the raiser will find that he can do this 

 without in any way injuring the stigma. This done, he should 

 affix to the stalk of the cyme a label stating the name of the 

 maternal variety and the date of sterilisation. It is advisable 

 that the forceps should be sterilised by re- dipping in the alcohol 

 after each separate bud has been dealt with, lest any of the 

 anthers may have been prematurely ripe and shed pollen on to 

 the forceps, which might •thus be accidently conveyed to the 

 stigma of the next flower. The bud having now been 

 sterilised and the label affixed, the next step is to preserve it 

 against contamination by insects.- This is done by placing 

 the group of buds within a parchment bag. The bag should 

 be opened over the end of a round stick and on no account 

 should it be blown into. WTien opened it is placed carefully 

 over the buds, and the edges of the bag brought firmly together 

 in a cluster round the stalk, and secured in that position by 

 winding some of the copper wire already described around the 

 neck of the bag. The label should be allowed to hang outside 

 the bag. 



Fertilisation.— If the weather is warm the buds within the 

 bag will open fully from within 24 to 48 hours, and it is when 

 they are open that fertilisation should take place. The most 

 opportune time is when the stigma has the shiny and sticky 

 secretion on it, but successful results may be obtained when 

 this is absent. Probably the best time of the day is between 

 10 .0 a.m. and mid-day, since as the day begins to cool the petals 

 close and the flower is more difficult to manipulate and possibly 

 not so ready to be fertilised. 



Having selected the paternal parent the operator should 

 remove the open flower and carry it to where the female plant 



