COLOURS OF FLOWERS AS A MEANS OF ATTRACTING ANIMALS. 191 



flowers with finely -marked petals are ardently souglit for, indeed, almost exclusively, 

 by flies. Many Orchids and Labiate flowers, but especially many Saxifrages 

 (Saxifraga Aizoon, aizoides, bryoides, rotitndifolia, stellaris, sarmentosa, &c.), are 

 very instructive examples. We cannot, indeed, explain what connection there is 

 between the visits of flies and the yellow, red, or violet dots which in some species 

 sometimes change their colour during the period of flowering. But it is certain 

 that the minute red and yellow spots on the petals of these Saxifrages do not 

 make the flowers more visible or conspicuous to the human eye. 



A brilliant contrast is caused by the difierence in the colours of the corolla and 

 the adjacent outspread bracts and sepals. The flower of Acanthus, whose upper 

 sepal is coloured violet, while the petals below it are white, deserves special notice 

 in this connection. Also those of Clcrodendron sanguineum with white sepals and 

 blood-red petals, as well as the inflorescence of many species of the Cow-wheat 

 {31elanfipyrum arvense, grandifioruni, nernorosuni), whose blossoms are yellow and 

 the bracts blue, violet, or red. Lastly, we may mention Sideritis montana and 

 BowMna, whose small, brown petals project like dark points from the yellow bracts. 



In the capitula of Composites whose flowers are crowded closely together, the 

 florets of the ray and of the disc usually display difierent colours. As examples 

 of this common form of colour-contrast may be mentioned the Ox-eye Daisy 

 {Leucanthevium vulgare), whose yellow disc -flowers are surrounded by white 

 ray -flowers; Pyrethruni carneum,, with yellow disc-flowers and red ray -flowers; 

 Rudbeckias and Zinnias {Rudheclda laciniata, fvdgens, Zinnia hybrida, &c.), whose 

 dark-brown disc-flowers are surrounded by yellow ray-flowers, and almost all the 

 numerous series of Asters with yellow disc-flowers and blue ray-florets. 



Contrast of colour is also frequently produced by the corollas changing their 

 colour at various stages of development. In the bud they are red, after opening 

 they become violet, and then when they wither they become blue or malachite 

 green. When such flowers are crowded together a very effective colour-contrast 

 may result. Especially remarkable in this respect are the Bitter Vetches (Orobus 

 vemus and Venetus), and several Boragineous plants belonging to widely difl^erent 

 genera (e.g. Pulmonaria officinalis, Mertensia Sibirica, Symphytuyn Tauvicum), 

 and also some Willows (e.g. Salix purpurea, repens, Myrsinites), in which latter 

 the crowded anthers appear at first purple, red, then yellow, and finally black. 

 The tubular flowers of the flat disc-shaped head of Telekia (TeleJda speciosa) are 

 yellow at first, but later become brown, and since the flowers open successively 

 from the circumference towai-ds the centre of the head, when the blossom is at its 

 height the yellow centre is surrounded by a dark-brown ring. In many species of 

 Clover (Trifolium), the faded corollas do not fall oflf at the end of the flowering 

 period, but wither and dry up, and envelope the small fruit like a mantle. The 

 stalks of the flowers grouped into umbellate heads then bend downwards and 

 arrange themselves into a wreath surrounding the upper, younger flowers which 

 stand erect and are, of course, of a different colour. Thus in the Bastard Clover 

 (Trifolium hybridum), the young, erect, densely-crowded, white flowers are 



