
LIFE STORY OF THE SWEET PEA 187 
they need the help of sunlight. They have been making 
starch. At night the starch is digested and changes to 
sugar. It flows to all parts of the plant where growth 
is taking place and new plant substance is wanted. 
We know that if the pea plant were grown in the dark, 
all the plant sub- 
stance it would 
have to use in 
growth would be 
that which was al- 
ready in the seed. 
The stem would be 
for a time long 
and slender, the 
leaves would be 
small and yellow- 
ish, and the frame- 
work of the plant | | 
would be soft. Tt FIG. 227. Sweet-pea stems needing support. 
would soon die. But in the light the leaves are green. 
We know that the carbon dioxid of the air gets into 
the green leaf. The light then helps the leaf to make 
the starch from which most of the new plant substance 
comes. 
Flowering time. The plant has now formed a strong 
working system, and its numerous branches bear many 
working leaves. It is prepared to flower. Since the 


