32 TROPICAL AGRICULTURE CHAP. 



The arrange- flowers, or even in different trees, some trees, as in the case 



Stamens 'and of the nutmeg, producing staminate or male flowers, and 



pistils. others producing only pistillate m female flowers. When 



this happens the plants are called dioecious, and fertilisation 



can take place only by the wind blowing the pollen on to 



the stigmatic surface of the pistils, or by insects and other 



animals carrying the pollen from the male to the female 



flowers. 



Fertilisation FERTILISATION BY WINDS. The date palm, the fruit of 



of the date 



palm. which forms a very important portion of the food supply of 



many of the inhabitants of western tropical Asia and north 

 Africa, is a dioecious tree usually fertilized by the agency 

 of winds : and the people often secure a good crop of dates 

 by climbing the female trees and shaking the pollen of the 

 male flowers upon the female ones. Indeed, it has been 

 recorded that some of the nations of Africa, when at war 

 with each other, destroy their enemies' male date trees, 

 which are much less numerous than the female ones, and by 

 this means bring about a famine in the land. A female 

 palm tree once grew in a hot-house in Berlin for eighty 

 years without bearing fruit, when, on it becoming known 

 that a staminate tree of the same species was flowering in 

 Dresden, some of the pollen was sent for by post, and 

 when it arrived it was sprinkled over the pistillate flowers 

 with the result that the tree became fruitful and bore a crop. 



Wind-blown i n cases where the pollen is carried by the wind for the 



pollen. 



fertilisation of flowers, it is exceedingly dry and light so 

 that it may be wafted to long distances. A wonderful illus- 

 tration of fertilisation by wind-carried pollen occurred in 

 Italy. A palm tree grew in Otranto, it bore year after year 

 many pistillate flowers, but no fruit was produced, al- 

 though the tree was healthy and vigorous. After many 

 seasons, a male tree of the same species blossomed at 

 Brindisi, and soon afterwards the tree at Otranto was laden 

 with fruit. The wind had carried the pollen a distance of 



