PRESIDENTIAL ADDRESS. 571 
On the other hand, adaptation, with its consequence of parallel or even con- 
vergent development in distinct stocks, is an insistent problem. The real ques- 
tion is, What causes are at work to produce such results? They are usually set 
down to the selection of favourable divergences from type out of those produced 
at random. But the prevalence of parallelism and convergence suggests that 
those inheritable variations, which are now styled ‘Mutations,’ are not pro- 
duced at random. The facts enforce the question whether or not they are 
promoted and actually determined in their direction, or their number, or their 
quality, in some way, by the external conditions. Parallelism and convergence 
in phyletic lines which are certainly distinct impress the probability that they 
are. Until the contrary is proved it would, in my opinion, be wiser to entertain 
some such view as a working hypothesis than positively to deny it. Such a 
working hypothesis as this is not exactly the same as a ‘ mnemic theory,’ though 
it is closely akin to it. It may perhaps be regarded as the Morphologist’s pre- 
sentation, while the mnemic theory is rather that of the Physiologist. But the 
underlying idea is the same—viz., that the impress of éxternal circumstance 
cannot properly be ruled out in the genesis of inheritable characters, simply 
because up to the present date no definite case of inheritance of observable 
characters acquired in the individual lifetime has been demonstrated. Of 
course, I am aware that to many this is flat heresy. At this Meeting of the 
Association it amounts almost to high treason. I plead guilty to this heresy, 
which may by any sudden turn of observation be transformed into the true 
faith. I share it in whole or in part with many botanists, with men who have 
lived their lives in the atmosphere of experiment and observation found in large 
Botanic Gardens, and not least with a ‘former President of the British Associa- 
tion—viz., Sir Francis Darwin. 
It is noteworthy how large a number of botanists dissent from any absolute 
negation of the influence of the environment upon the genesis of heritable 
characters. Partly this may be due to a sense of the want of cogency of the 
argument that the insufficiency of the positive evidence hitherto adduced 
justifies the full negative statement. But I think it finds its real origin in the 
fact that in Plants the generative cells are not segregated early from the somatic. 
In this respect they differ widely from that early segregation of germ-cells in 
the animal body, to which Weismann attached so much importance. The fact is 
that the constitution of the higher Plants and of the higher Animals is in this, 
as in many other points, radically different, and arguments from the one to the 
other are dangerous in the extreme. Those who interest themselves in evolu- 
tionary questions do not, I think, sufficiently realise that the utmost that can be 
claimed is analogy between the higher terms of the two kingdoms. Their 
phyletic separation certainly dates from a period prior to that of which we have 
any knowledge from the fossil record. Let us give full weight to this fact, as 
important as it is indisputable. The early definition of germ-cells in the animal 
body will then count for nothing in the evolutionary problem of plants. More- 
over, we shall realise that the plant, with its late segregation of germ-cells, will 
present the better field for the inquiry whether, and how far, the environment 
may influence or induce divergences from type. From this point of view the 
widespread opinion among botanists that the environment in some sense deter- 
mines the origin and nature of divergences from type in Plants should com- 
mand a special interest and attention. 
I must now draw to a close. I have passed in review some of your more 
notable plants, and pointed out how the Australasian Flora, whether living or 
fossil, includes in unusual richness those evidences upon which the fabric of 
evolutionary history is being based. I have indicated how this history in certain 
groups is showing ever more and more evidence of parallel development, and that 
such development, or convergence, presses upon us the inquiry into the methods 
of evolutionary progress. The illustrations I have brought forward in this 
address clearly show how important is the positive knowledge derived from the 
fossils in checking or confirming our decisions. Paleophytology is to be prized 
not as a separate science, as, with an enthusiastic view restricted between 
blinkers, a recent writer has endeavoured to enforce. To treat it so would be 
to degrade it into a mere side alley of study, instead of holding it to be the 
most positive line that we possess in the broad avenue of Botanical Phylesis. 
An appreciation of such direct historical evidence is no new idea. Something 
