1920.] Cross-Fertilisatwn in Potatoes. 



139 



a few hours. Such plants are extremely bad subjects either 

 as male or female parents. Those whose buds fall in the 

 earliest stages are, of course, useless for cross-fertilisation ; 

 those whose buds do not fall until considerably later can be 

 used as female parents, but the chance of obtaining a successful 

 result is very small. As male parents such plants are useless, 

 for the pollen does not ripen till the flower is well open, and it 

 will be found that such flowers as do eventually open will have 

 no pollen. 



Another difficulty a potato raiser has is that a number of 

 excellent v?rieties which produce beautiful blooms bear anthers 

 which contain no pollen. A striking example is Up-to-Date. 

 Of such plants it is true that by infinite perseverance an 

 occasional flower — perhaps one in three thousand — can be 

 fertilised, but even so, very few seeds will result. On the other 

 hand, such plants are perfectly suitable as female parents and 

 may be fertilised with the pollen obtained from any variety. 



Importance of Observance of Technique. — In crossing any two 

 varieties it is presumed that the raiser has a definite object in 

 view and that he hopes to obtain offspring whose qualities will 

 bear some definite relation to those of the parents he is em- 

 ploying. It thus becomes essential that he shall be perfectly 

 sure that in making the cross the seed which arises is due to 

 the union of the pollen he has introduced with the ovules or 

 eggs of the mother plant. There must be no uncertainty as to 

 whether these maternal ovules have been fertilised with pollen 

 derived from their own anthers or with pollen possibly derived 

 from a neighbouring and different variety and carried to the 

 mother plant by a bee or other insect. It is therefore essential 

 that he should observe a certain technique, and it is this 

 technique which will now be described. 



The raiser should provide himself with {a) a pair of fine- 

 pointed surgical forceps about 3 J in. in length, (b) a small 

 narrow-necked (2 -ounce) bottle filled with rectified spirit, 

 (r) small shop labels about ij in. by i in. with a fine string 

 loop by which they can be attached to the stem of the flower 

 (such labels are used by jewellers and other tradesmen for 

 pricing small articles), (d) parchment paper bags about 9J in. 

 by 6 in. (such bags are spe(^ially made for the purpose by 

 Messrs. John Miller & ( o., Ltd., 322-334, St. George's Road. 

 Glasgow), and (e) copper wive ^^in. in diameter, which should 

 be cut into lengths of about 5 in. 



Sterilisation. — Having chosen the mothex plant, a cyme, or 

 bunch of flowers, should be selected, and all flowers already 



