*37 
Green.- — On Vegetable Ferments. 
higher plants we have to recognize essentially the same con- 
stitution, the differences between them only depending on 
differentiation, and consequent division of labour. In the 
lowly forms the great prominence of their metabolic decom- 
positions has obscured all their other functions, and they have 
been therefore regarded as possessing special properties. In 
the higher plants investigation has shown us that precisely 
similar decompositions can be brought about, not now by the 
whole plant-body, but by special cells or parts of it. The 
agent in the decomposition is the same, the conditions similar, 
and the resulting products are strictly comparable. Instead 
therefore of speaking of organised and unorganised ferments, 
we come to recognize in the effects of them both only the 
power of the living substance to effect chemical change. In 
its most primitive form this is always intracellular, and involves 
the actual taking part in the decomposition by the protoplasm 
itself. Just however as in the slow movements of amoeboid 
protoplasm we recognize something which in the higher and 
more differentiated organism appears as the contraction of 
muscular fibre, so in this interaction we see a property which 
becomes more highly differentiated in the formation of 
enzymes, which work sometimes within and sometimes with- 
out the cells in which they are produced, the latter being the 
most specialised. The reason for the production of these 
enzymes is not always evident ; in many cases it has been 
seen to be needful to induce decompositions at some distance 
from the seat of their formation, as when the embryo secretes 
them to acquire the contents of the endosperm in which it is 
embedded ; in other cases, as in various microbes, it may well 
be to enable the plant, as Wood has suggested, to protect 
itself from adverse influence by forming a more resistant 
cell-wall ; in many cases of intracellular enzyme-action, how- 
ever, the present state of our knowledge leaves the matter 
unsolved. 
