337 



shown for the siliceous Hawkesbury Sandstone formation by E. corymbosa, hcemastoma, 

 eapitellafa, Sieberiana, piperita, etc., and in E. hemiphloia and E. tereticomis for the 

 Wianamatta Shale, which contains a much lower percentage of free silica. Other 

 instances are given. 



Climatic divisions (of New South Wales) are discussed at p. 27, and they are 

 classified as (1) Coastal or semi-jungle ; (2) Mountain or cold type ; (3) Interior or semi- 

 arid. He goes on to say that, owing to physiographic conditions, a fourth, referred to 

 in his paper before the Asst. Assoc. Adv. Science in 1907 as Western Slopes, may be 

 added. He alludes to E. cariacea attaining the highest altitude under No. (2), and 

 E. albens being typical of zone No. (4) which, in New South Wales, has an annual rainfall 

 of about 26-27 inches (see p. 29). 



At p. 48 he goes on to say — " Species having the various types of leaf venation appeal to exercise 

 some preference for different classes of geological formations. Those having the transverse venation 

 generally select the acid rocks which are composed of upwards of 70 per cent, silica, much of which is in a 

 free state. Species with the oblique venation are more, typical of the basic rocks and soils, although by no 

 means confined to that formation, some even growing on highly siliceous rocks. The trees with the parallel 

 (longitudinal) veins, such as E. dives, occupy chiefly the fairly siliceous formations or those containing 

 between 60 and 70 per cent, silica, but some of them grow on basic formations, while others are on highly 

 siliceous." 



See also E. C. Andrews, " Geographical Unity of Eastern Australia in late 

 and Post Tertiary time, with applications to biological problems," Journ. Roy. Soc, 

 N.S.W., XLIV, 420-480 (1910). 1 do not in this work, as a rule, take cognizance of 

 happenings in geological times, but the chapter " Biological Significance," at p. 466, 

 with its references to the evolution of the Eucalypts, will serve as an introduction to 

 the botanical deductions of this brilliant ■writer. 



ALTITUDE. 



Altitude above sea-level (and, of course, temperature varies with sea-level) is, 

 of course, one of the factors which determines the distribution of species. 



A species of Eucalyptus (coriacea) forms the tree-line at nearly 7,000 feet, a few 

 hundred feet below the summit of the highest mountain in Australia, Mount Kosciusko. 

 The trees at the highest elevations are remarkable for their bare stems, surmounted 

 with a dome or flatfish top of leaves. The bare stems are, doubtless, the consequence of 

 winds, the leaves being concentrated on the top as a thin " layer " and offering minimum 

 resistance to the wind. These dwarf trees are in masses of a fairly uniform height; 

 a different arrangement would result in the crown of leaves of the smaller plants being 

 beaten against the bare stems of their taller brethren, and denuded of their foliage. 

 The grotesque leaning forms of the stems, like guys or supports to resist wind-pressure- 

 are shown in my " Forest Flora of New South Wales," Part XV, p. 114. 



