Page:The Zoologist, 4th series, vol 2 (1898).djvu/412

380 known and undesirable garden moth, Abraxas grossulariata, in which the larva and pupa are both prominently marked with yellow and black, and the perfect insect exhibits the same prominent hues. Plants often develop colour in response to purely environmental conditions. Mr. Scott Elliot observes:—"I have noticed everywhere that in places.... where there is plenty of sunlight and not enough humidity to form a large amount of branches and leafage, the surplus nourishment is usually disposed of in bright colouring. A curious instance of this effect carried to extremes is an orchid (Disa erubescens, Rendle), which is all over the curious red colour which one often sees on the leaves and stems, e.g. of our common Herb Robert in England. Other instances of this sort of flora may be seen, e.g. on the limestone hillocks about Alexandria and on Table Mountain summit." Mr. Wallace enumerates as instances of colour needing "no special explanation," those algae and fungi which have bright colours—the "red-snow" of the Arctic regions, the red, green, or purple seaweeds, the brilliant scarlet, yellow, white, or black agarics, and other fungi; also the varied tints of the bark of trunks, branches, and twigs, which are often of various shades of brown and green, or even vivid reds or yellows. Prof. Marshall Ward also remarks:—"The red colour often assumed by parts of plants other than flowers, especially young leaves, afforded an instance of the danger of pushing an explanation too far. In many instances it doubtless served to absorb some of the sunlight, and so protect the chlorophyll of young organs; but such a case as the red colour in the lower layers of the floating leaf of a water lily demanded some other explanation.' Dr. Bonavia, amid much speculation, has truly written: "Phænogams, such as the carrot and beetroot, develop their orange and crimson colours in what we should consider as total darkness." We must all agree with Darwin that "hardly any colour is finer