Metaphyta L ilium. 1 69 



We have noticed already that the perianth leaves of the 

 lily are brightly coloured. We may now notice further 

 that they have a distinct odour, or scent. Lastly, an ex- 

 amination of the bases of the petals reveals the presence of 

 small disc-shaped glands, to which the name of nectaries are 

 applied, and which secrete a copious supply of nectar, a 

 sweet, sticky fluid, not unlike honey, and containing a large 

 amount of sugar in its composition. Everyone is familiar 

 with the fact that insects of various kinds, especially bees, 

 butterflies, and moths, visit flowers for the sake of this 

 nectar, which they use as food. Further, it has been 

 proved that they are attracted to the flower both by the 

 scent (produced by the evaporation of volatile oils) and by 

 the colour of the perianth. The insect in its movements 

 in the interior of the flower, whilst sucking the nectar, rubs 

 itself over with pollen, which when ripe tumbles out of the 

 open sporangia. The pollen grains are viscid and sticky 

 through having lain amongst the gelatinous tapetal cells. 

 The insect's back and legs are covered with hairs, to which 

 the viscid grains adhere. In this way the pollen grains are 

 conveyed to another flower, where they fall, or are rubbed 

 off by the insect, on the stigma. It is needless to say the 

 action of the insect in this matter is a quite unconscious one. 

 The stigma, it is to be remembered, is covered with hairs, 

 also viscid and sticky, and to these some of the pollen 

 grains adhere. They are nourished there by the secretion 

 in which they are caught, and in some way or another are 

 stimulated to further development. 



The development of a pollen grain consists in the ex- 

 trusion of part of its contents through the exosporium. The 

 protuberance gradually assumes the form of a long thread 

 or tube, the pollen tube, covered by the endosporium. 

 The pollen tube lengthens and bores its way through the 

 tissue of the style, and enters the micropyle of the ovule. 

 There the termination of the pollen tube swells, and its wall 

 becomes apparently more porous and suitable for the pass- 



