98 H. G. SMITH. 
may be connected in some way with the original establish- 
ment of the particular form and structure of the distinctive 
features which are characteristic of the species or group. 
The amount of manganese in the ashes of the timbers of 
all the species of the ‘‘Ironbarks’’ tested was in remark- 
able agreement, ranging from 1°5 per cent. in those of E. 
crebra and E. melanophloia to 1°15 per cent. in that of E. 
sideroxylon. If the presence of this element were an 
accident due to location of growth then there could not be 
this uniformity in percentage amount, and the presence of | 
Manganese in the soil in varying quantities may be thus a 
contributing factor to the distribution of these particular 
species. It is apparent, however, that manganese is a 
very widely distributed substance, for besides being found 
in all species of Callitris it most probably occurs in every 
species of Hucalyptus, and members of this genus extend 
over the greater portion of Australia. 3 
Those Hucalyptus trees which grow on the higher and 
poorer lands appear to contain less manganese in their ash 
than those which require a soil richer in ordinary mineral 
plant food, and this again may account somewhat for the 
position where certain Eucalyptus species grow. 
This question of the natural distribution of the Kucalypts 
is one which has had particular interest for scientists for 
along time. It may be, however, that species location is 
more largely due to chemical influences, and as our know- 
ledge extends in this direction it may be possible to give, 
eventually, a satisfactory explanation as to why certain 
species of Hucalyptus, under natural conditions, grow 
luxuriantly in one place but not in another. 
Mr. Cambage in his Presidential Address of last year 
brought forward considerable data, which added to our 
knowledge regarding this question of Hucalyptus distribu- 
tion, and directed attention to the influences certain soils 
appear to have on the location of members of the genus. 
