8 
INTRODUCTION. 
in solution, just as they came to the place where they have 
been stored, to the growing or respiring parts of the plant, 
or to form new reserve stores in another place. 
Respiration is continually going on in all living parts, and 
breaking down the protoplasm into simpler bodies. Besides 
this the plant forms many classes of products, some of which 
are apparently temporary reserves, others skeletal (fibres, 
&c.) or otherwise useful, others apparently waste products. 
The latter are sometimes excreted on the outer surface of 
the plant, but more often, however, retained in special re¬ 
ceptacles within the plant body. Among these products, 
whether useful to the plant or not, are many of great value 
to man, e.g., indiarubber, resins, gums, alkaloids, other 
drugs, &c. 
We may sum up this extremely fragmentary sketch of 
the chemistry of the plant in a graphic way, thus :— 
Water and dissolved bodies. Carbon dioxide gas, &c. 
Root. Green leaf. 
Food prepared in green leaf. 
_■ _A_ 
Plant body, composed of— Reserves— 
Living Protoplasm. Nitrogenous. 
Skeleton. Non-nitrogenous. 
Waste Products. 
Temporary reserve products. 
Other products useful to the plant. 
We may classify the products of plants on the basis 
afforded by the facts above sketched. Plants prepare from 
their food the following chief groups of products :— 
Living protoplasm. 
Skeletal substance—including fibres, cellulose (cell 
walls), woody tissues, &c. 
Reserve materials—nitrogenous, such as proteids, 
amides, &c. ; non-nitrogenous, such as carbo¬ 
hydrates (starch, sugar, cellulose, &c.), oils, &c. 
