POLLEN 233 



but if done with care it will always result as de- 

 scribed. One may make more certain of it by cover- 

 ing the flower with a small paper bag. 



The Palm which gives the edible date fruit, has 

 flowers of two kinds, borne on different palms. The 

 plants that is to say are dioecious, one kind having only 

 ovary flowers which ripen into the fruits, the other 

 only staminate flowers which do not produce fruit. 

 Many hundred years ago it was known to the Arabs 

 and to cultivators of Egypt, that the ovary flowers 

 would not produce fruits unless branches of the stami- 

 nate flowers, when newly opened and shedding pollen, 

 were placed near them. From this there arose a reli- 

 gious ceremony in which flowering branches of the 

 staminate palms were placed (or waved sometimes with 

 suitable incantations), so that the yellow pollen dust 

 might fall on the newly opened ovary flowers. What 

 exactly is the nature of pollen and how it causes 

 the formation of the seed and fruit, is now known to 

 science. If we put a few pollen grains in a solution 

 containing about 3% of sugar (the exact amount 

 differs with different flowers) and examine them in the 

 course of a day or two with a good lens, we shall find 

 that from most of the grains fine threads, which 

 are really very narrow tubes, have grown out. This 

 is what happens on the stigma. The pollen grains 

 .are caught on the sticky sugary surface, and the tubes 

 growing out in the same way, pass downwards through 

 the style and into the ovary, and there each makes 

 its way to the micropyle of an ovule, into which it 

 discharges part of its contents (two ' nuclei ') and then, 

 but not till then, the ovule starts to become the seed. 



