664 THE POPULAR SCIENCE MONTHLY. 



the ancestral creatures not then fully developed into anything that we 

 could distinctively call a bee or a butterfly. But, as the insects flew 

 about from one head to another in search of such food, they carried 

 small quantities of pollen with them from flower to flower. This 

 pollen, brushed from their bodies on to the sensitive surface of the 

 ovaries, fertilized the embryo seeds, and so gave the fortunate plants 

 which happened to attract the insects all the benefits of a salutary 

 cross. Accordingly, the more the flowers succeeded in attracting the 

 eyes of their winged guests, the better were they likely to succeed in 

 the struggle for existence. In some cases, the outer row of stamens 

 appears to have become flattened and petal-like, as still often happens 

 with plants in the rich soil of our gardens ; and in these flatter sta- 

 mens the oxidized juices assumed perhaps a livelier yellow than even 

 the central stamens themselves. If the flowers had fertilized their 

 own ovaries this change would of course have proved disadvantageous, 

 by depriving them entirely of the services of one row of stamens ; for 

 the new flattened and petal-like structures lost at once the habit of 

 producing pollen. But their value as attractive organs for alluring 

 the eyes of insects more than counterbalanced this slight apparent dis- 

 advantage ; 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 alluring the fertilizing flies, 

 they have secured the great benefit of perpetual cross-fertilization, and 

 so have 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 com- 

 posed 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 distinctive facts which peculiarly con- 

 cern the ancestry of the lilies and cereals. It is probable that the 

 nearest modern analogue of the earliest petal-bearing trinary flowers 

 is to be found in the existing alisma tribe, including our own English 

 arrowheads and flowering rushes. As a rule, indeed, it may be said 

 that fresh-water plants and animals tend to preserve for us very ancient 

 types indeed ; and all the alismas are marsh or pond flowers of an ex- 

 tremely simple character. They have usually three greenish sepals 

 outside each blossom, inclosing one whorl of three white or pink petals, 

 two or three whorls of three stamens each, and a number of separate 

 ovaries, which are not united, as in the more developed true lilies, into 

 a single capsule, but remain quite distinct, each with its own individ- 

 ual stigma or sensitive surface. Even within this relatively early and 

 simple group, however, several gradations of development may yet be 

 traced. I incline to believe that our English smaller alisma, a not un- 



