674 TRANSACTIONS OF SECTION M. 
Returning to the purely scientific aspects of research, the whole of existence is 
based upon the fundamental process by which the green leaf utilises the energy 
of the light falling upon it to split up the carbon dioxide of the atmosphere 
and transform it into those fundamental carbon compounds—sugars, starches, 
&c., which build up the substance of the plant. The animal creates nothing; it 
is only a transformer, and rather a wasteful one at that, of the compounds 
initially built up by the plant. Now, though the leaf is thus the prime creative 
force, it is yet a comparatively ineffective machine for dealing with the energy 
contained in the light, for it does not succeed in storing up in the shape of plant 
materials it produces as much as one per cent. of the energy that falls upon it as 
light, and in bright, tropical light the percentage utilised is even less. A steam 
engine, given a certain amount of energy in the shape of coal, turns out again 
about one-seventh of it in the shape of useful work; a gas or oil engine is an 
even more effective transformer. Can the duty of the leaf be increased so that it 
shall effect a greater production of dry matter for the amount of light energy it 
receives? We know very little as yet about even the sequence of chemical 
changes in the leaf beyond the fact that we begin with carbon dioxide and water 
and end with oxygen and some sort of sugar ; we are beginning to acquire know- 
ledge as to the extent the rate of change is affected by the supply of light, carbon 
dioxide, and water, and by the temperature. But we have now many examples 
in chemistry of reactions being speeded up or rendered more complete by means 
of some adjustment of the external conditions, so it is perhaps not too much to 
expect that this fundamental process of carbon accumulation may also be tuned 
up until the leaf becomes of greater efficiency than at present in producing tissue 
from the materials and energy supplied to it. 
Probably the most immediate successes are before the plant-breeder, now 
that the application of the Mendelian theory has provided a method which 
renders both speedy and certain the processes of crossing and selection whereby 
the practical men of the past, working almost at haphazard, have already 
effected such enormous improvements in our cultivated plants. Among cereals, 
the qualities in demand, qualities which we know to be obtainable, are resistance 
to disease, stiffness of straw, and a large migration factor. We want to get rid 
of the plant-doctor, as it were; spraying and other prevention or curative treat- 
ments are both costly and of limited efficacy ; the desirable method is to keep the 
plant free of disease by means of a naturally resistant constitution, and by 
establishing healthy conditions of soil and nutrition. As to stiffness of straw, 
the incapacity to stand up is probably the chief cause which limits the yield of 
corn crops in Britain wherever the farming is high. When a man keeps much 
stock, and buys cake either for his bullocks, or to feed to his sheep on the 
turnips, the land becomes so rich that the first corn crop will only stand up under 
exceptionally favourable weather conditions, and the farmer, so far from buying 
more fertiliser, cannot take full advantage of what is already in the soil. The 
land is often rich enough to yield 60 bushels of wheat to the acre, but it is 
exceptional that a crop of such weight will stand up so that it can be harvested 
by a self-binder. Mr. Beaven, in this section, has already dealt with migration ; 
clearly it is a matter of great importance to the plant-breeder. Though the 
details have only been worked out for barley, the different varieties of any culti- 
vated plant, wheat for example, are very much alike as regards their gross 
productive power—1t.e., the whole material grown weighs much the same in a 
dried condition. Even different crops produce much the same amount of dry 
matter when grown under the same conditions, this gross productive power being 
in all cases the similar product of the environment—i.ec., the result arising from 
the supply of food, water, light, temperature, &c. But granted that the different 
crops possess this same gross productive power, then their comparative usefulness 
depends upon the greater or less completeness with which they transform the 
crude material into products that may be used as food for man. In the cereals, 
for example, we want as much as possible of the original stuff manufactured 
by the leaf to be migrated later in the plant’s life into the seed; of the total 
weight of the crop we want the largest possible proportion to be high-grade grain 
and not low-grade straw. Mr. Beaven has shown that the various varieties of 
barley do differ constantly in their proportion of grain to straw, and as, without 
