138 Cross-Fertilisation in Potatoes. [may, 



THE TECHNIQUE OF 

 CROSS-FERTILISATION IN POTATOES- 



Redcliffe N. Salaman, M.A., M.D. 



Large mmibers of potato growers who are also potential raisers of 

 new varities of potatoes may find the following notes on the 

 technique of cross-fertilisation of interest and value to them 

 in their work. The operations of cross-fertilisation described 

 might usefully receive the consideration of agriculturists. 



Construction of the Flower. — The well-known flower of the 

 potato plant is hermaphrodite, that is to say, both male and 

 female elements are contained in one and the same flower. 



The Female Organs. — In the centre of the flower is an ovary 

 from which there projects a thin, green rod, the pistil, which 

 terminates in a cushion -like knob known as the stigma. \^Tien 

 the flow^er is ripe for fertilisation a slight sticky secretion appears 

 on the stigma. The shape of the stigma varies in difierent 

 potatoes, being notably cleft like a hot cross bun in some 

 W'hile quite small and round in others. 



The Male Organs. — Ranged round the ovary are five yellow 

 anthers on short, thick stamens ; each anther is made up of two 

 lobes. On the inner side of the anther each lobe will be seen 

 to have a longitudinal depression (line of dehiscence) to its 

 outer side, and as the anther ripens this depression ends in a 

 small aperture on the inner side of the apex of each lobe. It 

 is from this aperture that the pollen escapes. In nature the 

 stigma is fertiHsed by the pollen of its own flower, which 

 reaches it by being scattered from the anther through the small 

 hole and falling on to the ripe stigma. It is found, however, 

 that insects of all sorts freely visit potatoes when in bloom, and 

 bees will undoubtedly hover over the flowers and carry pollen 

 from one plant to another, so that in cross-fertilisation for 

 scientific purposes it is necessary to take certain precautions 

 which will be dealt with in detail later. 



Difficuitiee In Croes-Fertillsatlon.— It is common knowledge 

 that many potato plants form buds which never open, or at 

 least fall before the flower opens. . As a matter of fact varieties 

 differ very much in respect to this property. There are some 

 whose buds fall when they are no more than | in. long ; there 

 are others whose buds will grow till they reach a length of J in, 

 or more and then fall ; others, again, will bear buds which 

 actually open and form flowers, but these flowers drop within 



