198 INSECTS AND MAN 



the trees, cause sickness inducing disease, and eventually 

 destroy the plants. No such indictment can be brought 

 against bees. Again, these marauding insects cannot easily 

 be introduced into a neighbourhood, and when introduced 

 it is still more difficult, should occasion arise, to eradicate 

 them. Bees are domestic and social; their numbers may 

 easily be increased or diminished as occasion demands. 



Let us consider, for a moment, how this work of fer- 

 tilisation is carried out. For a clear understanding of the 

 process it is necessary to know a little about flower struc- 

 ture. The essential organs of a flower are the stamens and 

 pistil, and they are usually found in the same flower; 

 though, in certain cases, some flowers may be provided 

 with stamens and others with a pistil. The stamens may, 

 for our purpose, be considered as the male reproductive 

 organs, and they usually consist of two parts, a thread- 

 like filament and a terminal portion, the anther, which is 

 yellow in most plants ; sometimes the filament is absent. 

 The pistil, or female reproductive organ, is composed of 

 three parts, the terminal stigma, the central style, and the 

 basal ovary ; but often the style is absent. When the 

 anthers are mature they split open, and pollen, having 

 the appearance of very fine dust, escapes. The pollen is 

 carried by insects, wind, or more rarely by other agencies, 

 to the stigma of another flower, and, after various changes, 

 the little structures, called ovules, contained in the ovary 

 become seeds, and the ovary itself becomes the 'fruit. In 

 order that good, strong, healthy fruit may be produced it 

 is necessary that self -fertilisation should be avoided, that 

 is to say, the pollen from the anthers of a certain flower 

 should not fall on the stigma of the same flower, though 

 nature often makes provision for self-fertilisation, when 

 cross-fertilisation, as it is called, has failed. Pollen may 

 be red, white, green, or orange yellow the latter is the 

 prevailing colour. If a piece of honeycomb, containing 

 bee-bread, be cut in two longitudinally, strata of various 



