COLOUR OF THE FOLIAGE. .'31 



years, but remain in a withered or effete state on the principal axial 



growths for a much longer period. 



The. colour of the foliage is also worthy of note. From the deep 

 sombre hues of the Austrian Pine and Common Yew to the light 

 and airy deciduous Cypress and Maiden-hair Tree, the silvery lines of 

 the Weymouth Pine and the greyish foliage of Cupressus pisifera var. 

 xyuarrosa, there is found in the different Tribes an endless variety of 

 tints which the green of Xature alone displays. The deep glossy 

 green of the leaves of Abies bradeata renders that remarkable tree 

 distinct from every other Abies. The pleasing glaucous hue of the 

 Deodar Cedar is almost unique, and the rich deep colour of Libocedrus 

 tlecurrens is scarcely less so ; Pinus radiata is distinguished among all 

 Pines by its cheerful grass-green foliage which affords a striking contrast 

 to the dull grey hues of many of its congeners ; the difference in 

 colour between Abies nobilis and A. Nordinanniana is not less marked. 

 The foliage of Cryptomeria eleyans changes in winter to a deep bronzy 

 ^reeii tinged with crimson which makes this plant particularly ornamental 

 at that season, and a similar change takes place in Cupressus thyoides 

 var. ericoides, 'which becomes violet-purple.* The common Arbor Vitae 

 is brownish green, while varieties of the Chinese species have their 

 foliage of a rich golden yellow during the growing season. Many of 

 the Jumpers have a bluish glaucous tinge peculiar to them, and others 

 are quite grey. 



Besides the difference in -tints above sketched, the foliage of coni- 

 ferous plants is subject to two changes in colour, viz., VARIEGATION and 

 GLAUCESCENCE. Variegation is due to changes taking place in the minute 

 granules called chlorophyll bodies imbedded in the protoplasm of the 

 cells of the leaves (and stems) immediately beneath the epiderm or 

 skin, and which gives the foliage not only the prevailing green, but also 

 other tints as purple, crimson, brown, etc., characteristic of the foliage of 

 certain plants when in active growth.! Variegation shows itself in the 

 young growth of the plants, which, instead of appearing in the shade of 

 green natural to the species, takes some shade of yellow that varies in 

 the different kinds from a deep golden hue to a creamy white. In some 

 cases the whole of the newly-formed branchlets with their foliage is pro- 

 duced coloured. As the season advances, the tint gradually changes, first 

 by becoming deeper, then taking a perceptible shade of green, and finally 

 in the course of the second season, assuming the green natural to the 

 species, but not till a new coloured growth is formed. This kind of 

 variegation is observed to be tolerably constant in whatever description 

 of soil the plant is growing, but the intensity of the colouring is 

 slightly different in different soils, being most developed in clayey loams 

 In other cases the tips of a portion of the branches only appeal- 

 coloured, the extent of the variegation ranging in different and in the 

 same species from a mere spot to a considerable portion of the branch, 

 It is only in this form that a white variegation appears. Plants 

 * The foliage of all or nearly all the Coniferae of temperate climates cnanges colour 



in winter more or less. This is due to the low temperature of that season, which 



causes a peculiar transformation of the blue-green constituent of chlorophyll. A higher 



temperature restores the normal condition. 



t The giving of colour to the foliage of plants is a subordinate function of chlorophyll. 



Under the influence of sunlight it is the agent that converts the inorganic matter taken 



up by the roots, and the carbonic acid absorbed from the atmosphere, into the organic 



matter of which the plant is built up 



