7 8 



THE BOOK OF NATURE STUDY 



has been laid on the use of hairs. It is owing to the stigmatic 

 surface being covered with hairs that the pollen grains are kept 

 firmly on the stigma, whilst the pollen tube is being put out. In 

 fact, there seems to be a definite relation between the length of 

 the hairs and the size of the pollen grains. 



Insects are often entrapped by hairs, in order to ensure cross 

 pollination. The common plant called " Lords and Ladies " 

 (Arum maculatum) shows this very well. Small flies are attracted 



by the dark red spadix on which the 

 flowers are borne, by the smell, and 

 some may fly to the plant for shelter 

 in the large green bract (spathe). They 

 creep down until they reach the upper 

 part of the chamber formed by the 

 bending round of the edges of the bract. 

 Just on a level with the upper part of 

 this chamber the spadix bears hairs 

 which radiate outwards and allow the 

 insects to creep down, but not to get 

 out of the chamber. In reality, they 

 are imprisoned there until they have 

 done the work the plant requires from 

 them. In this plant the stigmas are 

 mature before the anthers. The flies, if 

 they have visited other Lords and Ladies, 

 will pollinate the stigmas with the 

 Then the stigmas 

 wither, and the flies get the honey 

 which is secreted on the tips of the 

 stigmas. Lastly, the anthers mature, the pollen sacs dehisce, 

 the pollen falls to the bottom of the chamber where the flies 

 still are, and they get dusted with it. Then the hairs shrivel 

 up and allow the insects to escape. These, laden with pollen, 

 if they fly to another Arum, will cross-pollinate it. One wonders 

 that any fly, having once tasted of this imprisonment, should 

 repeat the experiment ; but it seems certain from the large number 

 of flies found in the chamber of the Arum, that many must visit 

 one flower after another. Lord Avebury states that often more 



FIG. 44. Inflorescence of Arum 



maculatum. b, bract; ss, pollen brought, 

 spadix ; ^, hairs ; a, anthers ; 

 c, carpels. 



