INTRODUCTION. 
products. It may conduce to clearness, and save subsequent 
repetition if the general principles of the formation of pro¬ 
ducts in the plant be briefly described in this place. The 
ordinary green plant starts with the simplest materials, and 
from them elaborates complex products. It takes in water 
and simple salts dissolved therein from the soil by means 
of its roots, and takes in carbon dioxide gas from the air. 
From these simple substances it prepares its own food, the 
process taking place chiefly in the green leaves in the 
presence of air and sunlight. The food when prepared 
travels through the leaf stalks, stems, Ac., to the places 
where it is required for the building up of new plant sub¬ 
stance or the repair of waste. The living substances of 
which plants are largely composed are constantly being 
used up in respiration just as in animals, and require as 
constant renewal. The whole plant, however, does not 
consist of living respiring substance (technically known 
both in plants and animals as protoplasm). It may rather 
be looked upon, like an animal, as a mass of protoplasm 
arranged for working convenience upon a skeleton of fibres 
and cell walls, &c., which are not usually living. These are 
manufactured by the protoplasm out of the food supplied 
to it. 
The food may go directly from the leaves to be used in 
making new protoplasm and skeleton at the growing part 
of the plant, or it may be put by for a time in the form of a 
reserve upon which the plant will draw at a later period, or 
which it passes on to its offspring. Thus, the talipot palm 
fills its stem with an enormous mass of reserve food ready 
for its final burst of flowers, in forming which, and in provid¬ 
ing their seeds with reserves, the whole amount is used up. 
Nearly all plants supply their seeds with more or less stored 
reserve nutriment to keep the offspring growing until it has 
green leaves of its own, and can make its own food. In these 
reserves the plant always stores up both nitrogenous and 
non-nitrogenous materials. When required they travel away 
