331 



Then we have a phenomenon not yet worked ont — a steel-grey appearance, 

 such as is seen in the Blue-leaf Stringybarks (E. Icevopinea and agglomerata), 

 E. cneorifdia. We note it in the young leaves at the tips of the trees. It is akin to 

 the slight glaucousness of some of the preceding species, but may be in succession 

 to the anthocyanin colours of the young foliage referred to below. In this 

 connection we have the silky sheen of the leaves of E. drepanopJiyUa (see Part X, 

 p. 332). Some day the subject of lustre and colour in Eucalyptus will be taken up 

 by someone with a competent knowledge of physics. 



Speaking of the tropical Western Australia E. collina, Mr. W. V. Eitzgerald 

 writes that the branchlets and often the leaves appear as if covered with frost, becoming 

 so conspicuous that the trees can be seen from a long distance. 



Colour (Anthocyanin.) 



This pigment has been known for many years, but even yet its chemistry has 

 been imperfectly worked out {e.g., see Dr. M. A. Forster, F.R.S., " British Association 

 Report," 1921). It forms the pigment in the reddish or purple colour seen in the spring 

 foliage of the cherry, &c. It keeps back rays injurious to the plant, indeed, protects the 

 chlorophyll (see Kerner and Oliver). Support in favour of this view is found because 

 it is more abundantly deposited in parts exposed to light than those which are shaded. 

 Organs which are very thickly covered with hairs scarcely ever develop anthocyanin. 

 It is abundantly deposited in the young topmost branchlets of Eucalyptus trees, shining 

 in the bright Australian sun. It is a very common practice for ladies to decorate their 

 houses with Eucalyptus-tree tops, especially when flowers are scarce, for they are 

 charmingly decorative. I give, with a few unimportant additions, a paper of mine on 

 the subject taken from Proc. Linn. Soc, N.S.W., xliv, 761 (1919). 



Most people have noticed, particularly during the winter and early spring, that 

 on the young branchlets, the foliage of Eucalypts is, in some species, of a brilliant colour, 

 shades of crimson and purple being the commonest. There are few allusions to the 

 character in botanical literature, one of the few being the following : — 



Then again, the red colour of new foliage, so commonly seen here, is an outward sign of adaptation, 

 in that the colour apparently acts as a screen to prevent the chemical rays of light (blue end of the spectrum) 

 from penetrating the living workshops. Their admission to the young leaf cells would be detrimental, 

 whilst the heat rays (red end) are collected and thus secured as likely to help along the life processes more 

 rapidly to remove the new growth from babyhood to maturity.* 



Some years ago it entered into my mind to collect data as to the colours in 

 question, but I found practical difficulties arising from the fact that the colours that 

 we see on the living plant alter in tint within a few hours after removal. I then tried 

 taking the register of colours to the trees themselves, but found the standard work I 

 have adopted (Dauthenay's " Repertoire de Couleurs ") so heavy that it was out of 

 the question to carry it far in the bush. Accordingly, I submit some notes only on 



*C. T. Musson in " The Hawkesbury Agricultural Journal," 25th March, 1905, p. 68. 



