OcTOBER 9, 1902] 
NATURE 
583 
are contemplating original research. To my mind the possi- 
bilities of the living organism as such present a fascination which 
is not afforded by the dry bones of morphology or histology ; 
valuable as researches into the latter are, they seem to me to 
derive their importance very largely from the past, from the 
possibility of indicating or ascertaining the line of descent of 
living forms and the relation of the latter to their remote 
ancestors. The interest thus excited seems to me to be rather 
of an academic character when compared with the actual 
problems of present-day life, its struggles, triumphs and defeats 
in the conflict for existence waged to-day by every living organ- 
ism. The importance of the study of physiology as bearing 
upon the problems of the morphologists has, I need hardly say, 
been fully recognised by the workers in that field. I may quote 
here a sentence or two from the Address of one of my distin- 
guished predecessors, who said at Liverpool, ‘‘ There is a close 
relation between these two branches of biology, at any rate to 
those who maintain the Darwinian position, for from that point 
of view we see that all the characters which the morphologist 
has to compare are, or have been, adaptive. Hence it is im- 
possible for the morphologist to ignore the functions of those 
organs of which he is studying the homologies. To those who 
accept the origin of species by variation and natural selection 
there arg no such things as morphological characters pure and 
simple. There are not two distinct categories of characters—a 
morphological and a physiological category—for all characters 
alike are physiological.” 
But apart from the considerations of the claims of vegetable 
physiology based upon its own intrinsic scientific value and the 
interest which its problems possess for the worker himself, and 
upon the place accorded to it as its relationship to morphology, 
it must, I think, be recognised as being of fundamental economic 
importance, especially in these times of agricultural depression. 
For many years now it has been recognised that agriculture is 
based upon science ; that it involves indeed properly the appli- 
cation of scientific principles to the cultivation of the soil. But 
when we look back upon what has passed for agricultural science 
since the alliance between the two has been admitted, we can- 
not but recognise how lamentably deficient in breadth it has 
been. The chemical composition of the soil and subsoil has 
been investigated with some thoroughness in many districts of 
the country. The effect of its various constituents on the 
weight and quality of the crops cultivated in it has been ex- 
haustively inquired into, and a considerable amount of informa- 
tion as to what minerals are advantageously applied to the soil 
in which particular plants are to be sown has been acquired. A 
kind of empirical knowledge is thus in our possession, in some 
respects a very detailed one, quantitative as well as qualitative 
records being available to the inquirer. But elaborate as 
have been the researches in these directions, and costly and 
troublesome as the investigations have been, they have been 
hardly, if at all, more than empirical. Till quite recently the 
physiological idiosyncrasies of the plants round which all these 
inquiries centred were almost entirely ignored. No serious 
attempt was made to ascertain the way in whicha plant benefited 
by or suffered from the presence of a particular constituent of the 
soil. What influence, for instance, has potassium or any of its 
compounds upon the general metabolism of the plant? Does 
it affect all its normal nutritive processes, or does it specially 
associate itself with some particular one? If so which one, and 
how does the plant respond to its presence or absence by. modi- 
fying its behaviour? So with phosphorus again; hardly any 
investigation can be made into the nutritive processes of a plant 
without this element becoming more or less prominent. In 
some cases the empirical results already referred to show an 
enormous influence on the crop exerted by soluble phosphates 
in the soil or the manure applied to it. But what can yet be 
said as to the 7é/e played by phosphorus or by phosphates in 
the metabolic processes inthe plant? Further, how do different 
plants show different peculiarities in their reactions to these 
various constituents of the soil? For the advance of agriculture 
the study of the plant itself must now be added to the study of 
the soil. The fact that it is a living organism possessing a 
certain variable and delicate constitution, responding in par- 
ticular ways to differences of environment, capable of adapting 
itself to a certain extent to its conditions of life, dealing in par- 
ticular ways with different nutritive substances, must not only be 
recognised, but must be the basis for the researches of the future. 
which will thus supplement and enlarge the conclusions derived 
NO. 1719, VOL. 66] 
from those of the past, in some respects correcting them, in 
others establishing them on a firmer basis. 
In pressing upon the younger school of botanists the import- 
ance of this line of research, I do not wish to minimise the 
difficulties that accompany it. Difficulties of method assume 
considerable magnitude, for we have here no question of section 
cutting and microscopic examination. Vegetable physiology is 
allied very closely to other sciences, and research into its 
mysteries involves more than a preliminary acquaintance with 
them. Especially must one point out the importance, indeed 
the necessity, of acquaintance with a certain range of organic 
chemistry and with chemical methods of work. In certain 
directions, too, physics are as much involved as chemistry in 
others. The bearing of these sciences in particular directions 
will be referred to later. 
I fear another obstacle stands at the threshold of research 
which looks sufficiently formidable. The so-called fundamental 
facts of vegetable physiology have been laid down with sufficient 
dogmatism in text-books by many writers whose names carry 
with them such weight that it appears almost heresy to question 
their statements. We have been content to accept many things 
on the authority of the great workers of the past, with the 
result that the advance of knowledge has been hindered by such 
acceptance of what were deemed facts, but were really in- 
accuracies. We may refer, for instance, to the statement made 
by Boussingault, and accepted by most botanists ever since his 
time, that the absorption of carbon dioxide from the air takes 
place by means of solution in the cuticle of the epidermal cells 
of plants and thence passes by diffusion to the seats of photo- 
synthesis. Only comparatively recently has this been shown to 
be erroneous. If, however, it is once recognised that authority 
is fallible, this apparent obstacle becomes the opposite. The 
more evident questions have not yet been solved, leaving only 
the more difficult ones for the present-day worker. 
Recognising the importance of work in this field, and 
realising that with the advent of a new century new departures 
must be taken, I have thought I might venture to direct the 
thoughts of my hearers, many of whom T may call my col- 
leagues, to the present position of certain problems which have 
long been the subjects of speculation and which offer the pro- 
spect, if not of complete solution, at any rate of considerable 
advance if Mnvestigated by modern methods. 
I turn first to a few questions connected with the nutritive 
problems of plants in general 
There are several theories abroad as to the progress of events 
during photosynthesis, none of which can be regarded as en- 
tirely satisfactory. For many reasons it seems desirable that 
this question shall be thoroughly investigated in the light of the 
present condition of both chemical and physical science. I 
may perhaps venture to recall to you the principal hypotheses 
of carbohydrate formation which have been advanced, so that 
its present position may be properly appreciated. 
The view that has met with the widest acceptance is that o1 
Baeyer. On his hypothesis the carbon dioxide absorbed is 
decomposed under normal conditions to yield carbon monoxide 
and oxygen ; a corresponding and coincident decomposition of 
water leads to the production of free hydrogen and oxygen. 
The oxygen from both sources is exhaled, while the carbon 
monoxide and hydrogen combine to form formaldehyde. The 
formaldehyde gives rise by a process of polymerisation to some 
form of sugar. 
A modification 0. this hypothesis has been advanced, which 
suggests that the preliminary decomposition of the carbon 
dioxide and the water may not take place, but that by a rather 
less violent reaction between them the formaldehyde may be 
formed and the oxygen liberated. 
Erlenmeyer has suggested a somewhat different course of 
reaction, yielding substantially the same results. He thinks it 
possible that the first interaction of carbon dioxide and water 
leads to the formation of formic acid and hydrogen peroxide, 
and that these subsequently interact with each other, yielding 
formaldehyde and water and giving off oxygen. 
Many years after the views of Baeyer appeared, a hypothesis 
of a different nature was proposed by Crato. He suggests that 
the carbon dioxide after absorption becomes ortho-carbonic 
acid, and that this remains in solution in the cell sap. This 
acid has the structure of a closed benzene ring in which six 
molecules are linked together. This becomes decomposed, 
liberating six molecules of water and six molecules of oxygen, 
