THE BLANCHING OF CELERY 
293 
set, catnip, peppermint, wintergreen, and wormwood, for 
medicine. 
258. The Blanching of Celery is a practical application of 
the fact that chlorophyll cannot develop in darkness. The 
stalks are either covered with earth, or the rows of celery 
are shut in from the light by long strips of black paper which 
allow only the top leaves 
to project into the light. 
The white leaves in the 
heart of a head of cab¬ 
bage, lettuce, or in open¬ 
ing buds in the spring 
are also accounted for by 
the fact that they are 
shut off from light by the 
leaves which surround 
them. 
SUMMARY 
The leaf is the organ 
of greatest use to the 
plant in performing the 
processes which maintain 
its own life. In the leaf 
food is manufactured, digested, and assimilated. Its cells 
carry on excretion and respiration to a greater degree than 
any other cells of the plant. 
The purpose of the shape, size, and arrangement of leaves 
is to enable them to get the greatest amount of light and air 
possible. 
On the process of photosynthesis depends the whole 
world’s supply of food. 
QUESTIONS 
Name the processes carried on by the leaves. Which is of the great¬ 
est use to man? Why? What is the object of leaf arrangement? 
Figure 271. — Vertical Section of 
Cabbage. 
The thickened bases of the leaves are 
used for food storage. The stem of a 
cabbage is short, and the bud very large 
in proportion. Note the buds in the axils 
of the leaves. 
