320 



this provision Juts not boon so successful as the twisting of the leaf-stalk, for this species is a weakling and 

 rarely seems able to grow more than 20 feet high, and although in the past it appears to have had an 

 'extensive range at least from Bathurst to C'ooma, a distance of about 200 miles, it is not known in the 

 intervening area, and is looked upon as rare in both localities. The available evidence regarding this tree 

 points to the conclusion that it is probably a vanishing species. 



E. cordata of Tasmania is a very similar little tree and has adopted the vegetable wax instead of the 

 vertical' leaf . The species is confined to Tasmania, and even there is not regarded as plentiful. It seems 

 not unlikely that in the near geological future both these species will have disappeared. 



E. cinerea of the Goulburn district is somewhat similar to the two former, but appears to be past 

 the critical stage. It has covered its leaves with glaucous powder, and although some trees are furnished 

 with opposite orbicular and broadly ovate leaves only, others have developed many lanceolate leaves which 

 hang vertically. It grown to a height of 40 or 50 feet, has a fairly considerable range, and its stems are- 

 covered with thick, shortly-fibrous bark, while the two former have smooth bark. 



The remarks in regard to E. cinerea apply generally to an interesting species known as Silver-leaved 

 Iroiibark, E. melanophloia, except that the latter has a hard furrowed bark. (R. H. C'ambage, Proc. Roy. 

 tioc. N.S.W., xlvii, 39, 1913.) 



Glauceseence. — The clothing of the leaves with a glaucous powdery wax is often resorted by to the 

 Eucalypts, and especially by the juvenile foliage, but in many instances this method of protection is 

 adopted by the mature foliage as well and under different conditions of climate, from that of the hot and 

 dry interior to that of the cool mountain region, and also with varying degrees of intensity according to 

 the age of the leaves. This covering is largely met with in the cool climate, where it may be seen not only 

 on the leaves and buds, but also on the branchlets. and in some cases on the smooth-barked boles, as on 

 E. maculosa, Sieberiana, and rubida. As already pointed out (see Horizontal and Vertical leaves) it is the 

 method commonly availed of by those species whose leaves are sessile and orbicular to ovate (H. Deane 

 Proc. Linn. Soc. N.S.W., xxv, 471, 1900), and it appears to be a device adopted as a protection against 

 evaporation which may be caused either by the heat of the dry lowlands, or by the winds and intensity of 

 light in a clear atmosphere on the highlands. 



Thick Epidermis. — The thickening of the epidermis has already been referred to under " Thick and 

 Thin leaves." (ib.. p. 44.) 



There are factors which, induce variation in glaucousness, and it will require 

 many years of research before the facts are ascertained. The seasons and the climatic 

 conditions affect the amount. As has already been well ascertained, glaucousness 

 hinders transpiration, and therefore approach to the interior, and xerophytic conditions 

 generally regulate its amount. Conversely, hardly any members of the Renantherse 

 are glaucous; they are coastal. 



I make a beginning in offering a provisional list of species as regards glaucousness; 

 it will be a framework for observers to begin on. 



Glaucous only on the underside. 



The most marked species are :— 



E. globulus, E. Maideni, 



and they seem unique. 



Those which are simply paler on the underside are very much more numerous; 

 the pale undersides can be best studied from, seedlings, and I will draw attention to 

 the subject when I deal with those. 

 L 



