COLOURS OF PLANTS. 229 



less curious phenomena have since been found to occur 

 even among some of the most regularly-formed flowers. 

 The arrangement, length, and position of all the parts 

 of the flower is now found to have a purpose, and not 

 the least remarkable portion of the phenomenon is the 

 great variety of ways in which the same result is 

 obtained. After the discoveries with regard to orchids, 

 it was to be expected that the irregular, tubular, and 

 spurred flowers should present various curious adapta- 

 tions for fertilization by insect-agency. But even 

 among the open, cup-shaped, and quite regular flowers, 

 in which it seemed inevitable that the pollen must fall 

 on the stigma and produce constant self-fertilization, it 

 has been found that this is often prevented by a phy- 

 siological variation the anthers constantly emitting 

 their pollen either a little earlier or a little later than 

 the stigmas of the same flower, or of other flowers on 

 the same plant, were in the best state to receive it ; and 

 as individual plants in different stations, soils, and 

 aspects, differ somewhat in the time of flowering, the 

 pollen of one plant would often be conveyed by insects 

 to the stigmas of some other plant in a condition to be 

 fertilized by it. This mode of securing cross-fertilization 

 seems so simple and easy, that we can hardly help 

 wondering why it did not always come into action, and 

 so obviate the necessity for those elaborate, varied, and 

 highly complex contrivances found perhaps in the 

 majority of coloured flowers. The answer to this of 

 course is, that variation sometimes occurred most freely 

 in one part of a plant's organization, and sometimes 

 in another ; and that the benefit of cross-fertilization 

 was so great that any variation that favoured it was 



