PRESIDENTIAL ADDRESS. 29 
Dr. Cuthbert Hall informs me that he has experienced 
great difficulty with the seedlings of E. fastigata, E. 
dextropinea, and a few other species, and that he has been 
unable to grow the seedlings of these species beyond the 
second leaf stage, as with a very few exceptions they then 
all died, the soil apparently not being suitable. 
It is not possible, of course, to know the real extent of 
these influences until the chemistry of the species in its 
relation to the soil, on which it grows naturally, shall have 
been fully determined. Although the soil and its constitu- 
ents exert the chief influences upon the natural distribution 
of species, yet, altitude or climate, seems to be a con- 
tributing factor also. The conditions directing these 
influences are, however, at present very imperfectly under- 
stood, and it may be that one set of factors is the corollary 
of the other, both acting along parallel lines. | 
The marked differences in the characters and amounts 
of inorganic constituents which appear to be necessary to 
the natural growth of the different species, or rather groups 
of Kucalypts, arrests one’s attention; particularly when it 
is seen that there is roughly arelative constancy in require- 
ments with certain elements with the members of each 
group. This unconformity in mineral constituents with 
species belonging to different groups, but growing in close 
proximity to each other, seems to indicate that the solvent. 
action of the roots of the several species is not ofa uniform 
character, or else that certain of the mineral substances 
dissolved have a poisonous action upon some _ species, 
although necessary to the growth of others. Magnesium 
appears to be a necessary constituent for the growth of all 
species of Kucalyptus, and is one of the principal mineral 
constituents in the ashes of some of them. On the other 
hand calcium does not seem to be in such demand by the 
members of certain groups, although it is found in great 
