4 POLLINATION AND CROSS-FERTILISATION IN RlCE. 



and if at this stage the glumes are gently pulled apart, the 

 anthers may be seen to dehisce and the pollen to fall in 

 showers on to the feathery stigmas within. It is probable 

 that the pressure of the anthers — which at this stage are being 

 pushed up by the rapidly elongating filaments from below — on 

 the glumes, together with the slight shock caused by the opening 

 of the glumes and the consequent access of air and sunlight, 

 are the immediate causes which brino- about dehiscence. 



o 



Immediately after dehiscence, the glumes diverge a little 

 further apart, the filaments rapidly elongate till the anthers 

 protrude about their own length above the tip of the glumes, 

 and then bend slowly outwards and downwards so that the 

 anthers ultimately assume a pendent position. But before 

 this stage is reached, in every normal case the anthers have 

 already lost almost all their pollen and pollination has taken 

 place before they emerged at all. 



Both the extent to which the flowers open and the length of 

 time they remain open vary considerabl}^ but we have not been 

 able to discover any differences in varieties with regard to this. 

 It appears to be largely due to atmospheric conditions at the time. 

 In the warmer and moister months of May and June the Howers 

 of the Aus varieties open earlier in the morning, but appear to 

 open to a less extent, and to remain open a shorter time than in 

 the case of Aman varieties which flower in the colder and drier 

 months of October-November. According to our observations, 

 the whole process from the time of the opening of the glumes 

 and dehiscence of the anthers till the time when the latter 

 assume the pendent position, occupies on an average only about 

 fifteen minutes, in both Aus and A^nan varieties, but in the case 

 of Aus varieties the flowers seldom remain open for a longer 

 period than half an hour in all, while in the case of Aniait varieties 

 they may remain open for periods varying from about an hour to 

 an hour and a half. If the weather is wet and rainy at the time 

 when the flowers should normally open, as is frequently the case 

 when the Ans varieties flower, they may not open at all, or if 

 they do, they often do not close again, and a large percentage of 



