n] OF ANTHOCYANINS 23 



the meadows on the shore, and on the islands of the Danube, rise huge 

 abeles and black poplars, elms, willows, alders, and also an abundant 

 sprinkling of trees of the bird cherry (Primus Padus)....The first frosts 

 are the signal for the beginning of the vintage ; all is busy in the vine- 

 planted districts, and the call of the vine-dresser resounds from hill 

 to hill. But it is also the signal for the forests on the mountain slopes 

 and in the meadows to change their hues. What an abundance of 

 colour is then unfolded ! The crowns of the pines bluish-green, the 

 slender summits of the firs dark green, the foliage of hornbeams, maples, 

 and white-stemmed birches pale yellow, the oaks brownish-yellow, the 

 broad tracts of forest stocked with beeches in all gradations from 

 yellowish to brownish-red, the mountain ashes, cherries and barberry 

 bushes scarlet, the bird cherry and wild service trees purple, the cornel 

 and spindle-tree violet, aspens orange, abeles and silver willows white 

 and grey, and alders a dull brownish-green. And all these colours 

 are distributed in the most varied and charming manner. Here are 

 dark patches traversed by broad light bands and narrow twisted stripes ; 

 there the forest is symmetrically patterned; there again the Chinese 

 fire of an isolated cherry-tree or the summit of a single birch, with its 

 lustrous gold springing up among the pines, illuminates the green back- 

 ground. To be sure this splendour of colour lasts but a short time. 

 At the end of October the first frosts set in, and when the north wind 

 rages over the mountain tops, all the red, violet, yellow, and brown 

 foliage is shaken from the branches, tossed in a gay whirl to the ground, 

 and drifted together along the banks and hedges. After a few days 

 the mantle of foliage on the ground takes on a uniform brown tint, 

 and in a few more days is buried under the winter coat of snow." The 

 extreme beauty of the Alpine vegetation in autumn is also described 

 by Overton (333), and led him to investigate the cause of the coloration. 



Detailed accounts of the physiological processes producing autumnal 

 coloration will be given in Chapter vi. 



As in the case of reddening of young developing leaves, autumnal 

 coloration is by no means universal, since, as we have seen, there are 

 many trees and shrubs of which the leaves turn either yellow or brown 

 and show no trace of pigment (Fagus sylvatica, Carpinus Betulus, 

 Quercus Robur, Betula alba, Alnus glutinosa, Populus alba, P. nigra, 

 P. tremula). There is some indication of a general tendency among 

 genera of certain orders to develop red autumnal coloration, whereas 

 genera of other orders are without it. Thus, for instance, the trees 

 and shrubs of the Rosaceae (species of Pyrus, Primus, Rosa, Crataegus) 



