The Origin of \\ heat. 139 



selves. If the flowers had fertilised their own ovaries 

 this cliange would of course have prr.ved disadvan- 

 ta'^cous, by dcprivincj them entlrel}- of the services of 

 one row of stamens ; for the new flattened and petal- 

 like structures lost at once the habit of producin^r 

 pollen. But their value as attractive or^^ans for 

 alluring the eyes of insects more than countei balanced 

 this slight apparent disadvantage ; and the new petal- 

 bearing blossoms soon outstripped and utterly lived 

 down all their simpler petalless allies. By devoting 

 one outer row of stamens to the function of allurinji 

 the fertilising flies, they have secured the great 

 benefit of perpetual cross fertilisation, and so ha\e got 

 the better of all their less developed competitors. At 

 the same time, the exudations at the base of the 

 petals have assumed the definite form of sweet nectar 

 or honey, a liquid which is mainly composed of sugar, 

 that universal allurer of animal tastes. By this means 

 the plants save their pollen from depredations, and 

 at the same time offer the insects a more effectual 

 because a more palatable sort of bribe. 



Passing rapidly over these already familiar initial 

 stages, we may go on to those more special and dis- 

 tinctive facts which peculiarly concern the ancestry of 

 the lilies and cereals. It is probable that the nearest 

 modern analogue of the earliest petal- bearing trinary 



