COLOUR AT DIFFERENT ELEVATIONS. 511 



is actually destroyed by bright light in plants which are not properly screened, 

 and the green tissue is then blanched and assumes a yellow tint. Since the 

 intensity of the sun's rays increases with the elevation in mountain districts 

 (see vol. i. p. 525), we should expect that this effect of light would be shown 

 particularly well in plants of high elevation. And this is certainly the case. 

 The flowers of species grown in the Alpine garden on the Blaser at a height 

 of 2195 metres above the sea exhibited, as a rule, brilliant floral tints, and some 

 were decidedly darker than the flowers grown in the Vienna Botanic Garden. 

 Agrostemma Githago, Campanula pusilla, Dianthus inodorus (sylvestris), Gypso- 

 phila repens, Lotus corniculatus, Saponaria ocymoides, Satureja hortensis, 

 Taraxacum officinale, Vicia Cracca, and Vicia sepium are good examples of this. 

 Several species, which produced pure white petals in the Vienna gardens, e.g. 

 Libanotis montana, had petals coloured reddish-violet by anthocyanin on their 

 under sides in the Alpine garden. The glumes of all the Grasses which were 

 green, or only just tinged with violet at a low level became a dark brownish- 

 violet in the Alpine garden. The abundant formation of anthocyanin in the 

 green tissue of the foliage-leaves and sepals, and in the stem, was particularly 

 apparent. The leaves of the Stonecrops, Sedum acre, album, and sexangulare 

 became purple-red, those of Dracocephalum Ruyschianum and Leucanthemum 

 vulgar e violet, those of Lychnis Viscaria and Satureja hortensis a brownish- 

 red, and the foliage-leaves of Bergenia crassifolia and Potentilla Tiroliensis, 

 even in August, had the scarlet-red colour which they usually assume in sunny 

 spots in the valley in late autumn. I must not omit to mention that, according 

 to some of my zoological friends, many animals, especially spiders and snails, which 

 have been transferred from the plains to the mountain-heights, assume a darker 

 tint in alpine regions. 



A considerable number of plant species, especially those which grow in the 

 valley in shaded or half -shaded places, as, for example, Arabis procurrens, Digitalis 

 ochroleuca, Geum urbanum, Orobus vernus, Valeriana Phu, and V. simplicifolia, 

 Viola cucullata, developed more or less yellowish leaves in the Alpine garden, 

 where they were exposed to the full sunlight. It was mentioned in vol. i. p. 393, 

 that the Flax (Linum usitatissimum), which flourishes in mountain valleys 

 at a height of 1500 metres, where its chlorophyll is uninjured, nevertheless 

 turns yellow in the Alpine garden at a height of 2195 metres. 



From this general review of the modifications in plant-form obtained by 

 culture-experiments, a series of important conclusions may naturally be drawn. 

 In the first place we must point out that two kinds of characters are to be observed 

 in plants, those which are the result of certain conditions and properties of soil 

 and climate, and those which appear independently of these external influences. 

 This distinction is so important that we shall illustrate it by two examples. 

 The white Water-lily, Nymphcea alba, develops scale-leaves of ovate or lanceolate 

 shape with no separation into petiole and lamina. The foliage-leaves, however, 



