86 INTRODUCTION 



assemblage of flowers is considerably increased. As Herm. Muller (' Weit. Beob.,' 

 I, p. 299) states, the petals of Ribes sanguineum, which are pure white during 

 flowering, become an increasingly darker tint of rose red after the dehiscence 

 of the anthers, the pollination of the stigmas, and the cessation of nectar secretion. 

 The cunning bees however, which play the part of visitors, confine their attention 

 to flowers in which the corolla is still white. In Ribes aureum the petals, at first 

 bright yellow, assume a carmine red colour after the stamens and styles fade ; thus 

 serving the interests of the community, after their own fertilization has been secured, 

 by heightening the attractions of the whole. Similar relations are observable (op. 

 cit., p. 300) in Weigela rosea, Melampyrum pratense, Aesculus Hippocastanum, 

 species of Fuchsia, and others. 



According to Fritz Muller (Nature, xvii, 1877, p. 79) there occurs in 

 Brazil a Lantana with flowers that are red on the first day, orange on the second, 

 and purple on the third. 



According to Ludwig (Biol. Centralbl., vi, 1886) there is a remarkable colour- 

 change in the flowers of Veronica Sandersoni. The corolla is at first bright red, 

 while the filaments and style (about 7 mm. in length) are also red. Later on 

 these organs all become white, and the style attains a length of 13 mm. 



The most gorgeous example of colour-change (Ludwig, op. cit.) is that seen in the 

 melanostomaceous Pleroma Sellowianum, the flowers of which are at first of a pure 

 white, and later on of a purple red. In Spiraea opulifolia (Ludwig, op. cit.) the colour 

 continues to change even after fading, becoming most vivid in the ripening capsules. 

 In this case, therefore, the fruits as they mature assist in rendering the plant 

 conspicuous (Just's bot. Jahresber., Leipzig, xiv, (1886) 1888, pp. 806, 807). 



Most flowers become inconspicuous as soon as they have been fertilized, 

 assuming a dull colour, and either fading or falling off. The state of things 

 exemplified by the flowers referred to above, is only possible (Ludwig, op. cit., 

 pp. 299, 300) where pollination is effected by a limited set of insects, as otherwise 

 fruitless ransacking of the most conspicuous flowers would mean a great waste 

 of time, delay fertilization, and undoubtedly in many cases create a distaste in 

 the often deceived visitors, so that injury rather than benefit would result. Delpino 

 (' Ult. OSS.,' Atti Soc. ital. sc. nat., Milano, xvi, 1874, p. 28) was the first to give an 

 explanation of the colour-change in the flowers of Ribes aureum, suggesting that 

 flowers which are over are made conspicuous as such to visitors, which are con- 

 sequently spared useless work. According to Herm. Muller (' Weit. Beob.,' I, 

 p. 300) such change of colour cannot be the primary significance, for, if it were, 

 flowers exhibiting it would not have the least advantage over those that fade or 

 fall off immediately after pollination. There can be no doubt that the entire floral 

 assemblage is rendered more conspicuous by the persistence and more intense 

 coloration of the fertilized flowers, so that insects are attracted in greater numbers. 

 But obviously such an adaptation can only be of the greatest use if the fertilized 

 flowers are easily to be distinguished from the rest. 



Kerner('Nat. Hist. PI.,' Eng. Ed. i, II, pp. 194-5) calls attention to colour- 

 contrast between flowers and the ground. In and around woods the surface in 

 spring is brown or yellow, owing to the fallen leaves of the previous year. The 

 blue flowers of Hepatica triloba contrast admirably with such ground. ' On ploughed 



