148 BOTANY. [CHAP. iv. 



very clearly illustrated in our own wild violets. The 

 corolla in the violet is very highly differentiated for the 

 purpose of favouring insect-fertilization, although the 

 petals are not grown together, yet the corolla presents 

 the bilabiate type, with the lower lip standing out as a 

 landing-stage, there is a well-developed spur containing 

 nectar, and having the entrance guarded against the 

 entrance of small insects in a manner already described ; 

 the coloration passes in the various species from yellow 

 to very dark blue with just a tinge of red ; scent, as is 

 well known, is present in some species; in fact, the 

 whole structure of the flower shows that self-fertilization 

 was almost impossible, and that the visits of insects was 

 indispensable, yet all these elaborate arrangements have 

 not prevented the violets from evolving something even 

 more effectual and at the same time more economical in 

 connection with fertilization, and in reality the old- 

 fashioned coloured flower, evolved for aiding insect- 

 fertilization, is now of no use to the plant ; but, as pre- 

 viously explained, when a structure is evolved, it cannot 

 be at once arrested, even when completely superseded 

 and useless, and this is the condition that most of the 

 violets now find themselves in, encumbered with an old 

 effete type of arrangement for securing insect-fertiliza- 

 tion. The new type of flower present in many violets 

 appears later in the season than the old type of flower, 

 from which it differs fundamentally in being self-ferti- 

 lized, the sepals remaining closed until fertilization is 

 effected, petals are absent or rudimentary, the stamens 

 reduced to one or two, and containing only a small quan- 

 tity of pollen, but being placed in contact with the 

 stigma, fertilization is insured. These permanently 



