152 FIELD, FOREST AND FARM 



that the pollen 's indispensability is plainly manifest 

 on account of the natural separation of the stamens 

 and pistils. Let us take for example the locust, a 

 tree of extreme southern France, bearing seeds in 

 pods similar to those of the pea, but brown, very long, 

 and very wide, and containing in addition to the 

 seeds a sugary pulp. Supposing we took a notion, 

 if the climate permitted, to grow locust seeds in our 

 garden, what locust tree must we plant? Evidently 

 the one with pistils, because it alone produces the 

 ovaries that become fruit. But that is not enough. 

 Planted by itself, the locust tree with pistils will in- 

 deed blossom profusely every year, but will never 

 in all eternity bear any seeds, for its flowers will fall 

 without leaving a single ovary on the branches. 

 What is wanting? The action of the pollen. Near 

 the locust with pistils let us plant one with stamens. 

 Now fructification proceeds as we wish. Puffs of 

 wind, insects that pilfer from one flower and carry 

 to another — these convey the pollen from the sta- 

 mens to the stigmas, the torpid ovaries spring to 

 life, and the locust pods grow and ripen perfectly. 

 With pollen, seeds ; without pollen, no seeds. 



"Another example. In spots of fertile land in 

 Northern Africa, spots of land called oases, the 

 Arabs cultivate numerous date-trees which provide 

 them with dates, their principal food. Date-trees, 

 too, like the locust, are dioecious. Now, in the coun- 

 try of the date-tree, a sandy plain parched by the 

 sun, spots of watered and fertile land are rare and 

 have to be turned to the utmost possible account. 



