.34 CHAPTER IV 



{a) Sdj '-fertilization. This only occurs when the variety in question 

 produces, fertile pollen, and is only certain when but one variety is under 

 cultivation, or when the flowering season of different varieties is separated, 

 or when the flower is protected from wind-borne pollen by devices such as 

 muslin bags. 



(b) Cross-fertilization or Hybridization. Several methods are employed. 

 Drumm in 1869, in Barbados, put the flowers of different varieties 

 together in muslin bags and then sowed the arrows separately. The 

 female parent of any resulting seedling is then known, but the male parent 

 may be either of the two varieties bagged. 



To avoid the inconvenience of bagging the inflorescence, canes of different 

 varieties are planted in alternate rows, or in chess-board fashion, when again 

 an uncontrolled cross- fertilization may arise. In this method the number 

 of possible male parents is the number of varieties which possess fertile 

 pollen. 



The observation that some varieties do not produce fertile pollen led 

 Kobus to initiate the use of such varieties as the female parent ; and when 

 Drumm's technique is followed, or when only two varieties are grown or 

 are in flower simultaneously, hybrids of ascertained parentage result. 

 Sterility of the pollen is, however, only relative, and in this procedure some 

 element of doubt remains. 



The only sure method of obtaining seedlings of controlled parentage 

 is the emasculation of the flowers of one variety before the pollen is ripe, 

 followed by subsequent impregnation with the pollen of a second. 



This was first done in 1904 by Lewton-Brain 18 in Barbados, and by 

 Mitchell 19 in Queensland. In performing this operation an immature in- 

 florescence of the variety destined to become the female parent is selected, 

 and during a working day the stamens are dissected out from as many single 

 flowers as is possible. The rest of the" inflorescence is then removed and the 

 emasculated flowers protected from adventitious pollination by enclosure 

 in a fine muslin bag. After the stigmatic plumes have become ripe, pollen 

 from the variety selected to be the male parent is dusted on with a fine 

 camel's hair brush. 



The skill required, the uncertainty of the results, and the small number 

 of seedlings obtained, have prevented the extended use of this method as a 

 means of obtaining new varieties, though it is being followed up now in Java 

 and in the British West Indies in a study of the application of Mendelian 

 principles to cane breeding. 



In obtaining seedlings from naturally fertilized seed, it is customary 

 to collect the inflorescences when the spikelets begin to fall naturally. The 

 tassels are then hung up to dry, and after a few days the spikelets fall off, 

 or can be easily detached. After one or two more daj^s' drying they are 

 ready for sowing. The seeds are sown in boxes* In Hawaii it is customary 

 to use a rich vegetable mould collected from the neighbouring forest , this 

 is sterilized by boiling to kill seeds of other grasses. In India fine horse-dung 

 is well watered and any seeds present allowed to germinate. It is then 

 stored and when required for use mixed with equal parts of fine river sand. 

 The seeds generally germinate in less than a week, and when about two 

 months old are ready to be transplanted to flower pots or wicker baskets, 

 and eventually are planted out in the field, after which the process of selection 

 begins. 



