80 



THE ROLE PLAYED BY BEES IN FERTILIZATION 



OF FLOWERS. 



By. F.W.Iv. SLADEN, Assistant Entomologist of the Department of Ag- 

 riculture, Ottawa. 



The flower contains the reproductive organs of the plant, the organs 

 are sexual and it is necessary for the male element, the pollen grains — 

 to come in contact witih the female element — the ovules — in order that 

 the latter may produce seed. The pollen grains are shed by anthers which 

 are borne on slender threads called stamens. 



A rod called the pistil arises from the ovary, or vessel containing the 

 ovules, on the end of this is a protuberance, called a stigma, the surface 

 of which is sticky so that the pollen grains adhere to it. 



Here they germinate and spnd processes down the pistil whicli 

 enter the ovules and so fertilization takes place. 



The two chief agencies employed by plants to bring the pollen grains 



to the stigma are wind and insects. 



It should be noted that in some plants the sexes are in separate 

 flowers, but the majority of flowers are hermaphrodites e.g. male and fe- 

 male organs are in the one flower. These flowers would seem to be 

 easily self-pollinated, but as a matter of fact they depend mostly on in- 

 sects foir fertilization, for, not only is the pollen somewhat glutinous but 

 in many instances self-pollination is impossible. 



There are all kinds of speciial arrangements to prevent it, either the 

 anthers mature and shed their pollen before the stigma is receptive, as in 

 the cases of the willow herb ( Epilobium augustifolium ) the garden sage 

 (Salvia officinalis )! and the nasturtium ( Tropoeolum majus ) or that tne 

 stigma withers before the flowers are pollinated or before the anthers 

 burst, as in the case of the fig-wort. 



In some apparently hermaphrodite flowers, the anthers or the ov/arie.^ 

 are sterile, therefore they are uni-sexual. 



Some flowers, it is true, are absolutely self-fertile, the sweet-pea 

 (Ivathyrus odoratus ) for example, but there are many others that may 

 be able to pollinate themselves, yet they produce more abundant and bet- 

 ter seed when pollinated bv another llower. The structure of flowers ena- 

 bles insects to pollinate them. Nectar and pollen are offered in re- 

 turn for fertilization, and the insect is shown the way to them by means 

 of colors that contrast well with green, such as red, blues, purples, yel- 

 lows, the whites, not brown, which stand out on our railway signals, 

 sign-boards, etc. It is the petal of the flower that is usually colored. To 

 be effective signs, and seen at a distance, the flowers must be of good 

 size or massed together as is clover. 



A few flowers such as figwort have their nectaries more or less ex- 

 posed and the honey can then be collected by short tongued insects as 



