

146. THE BEHAVIOUR OF PLANTS 
the western horizon. For a week or more the sunflower 
head will face the sun directly and follow it all day as 
sun even though the leaves are 
cut away. 

Fic. 178. The young head follows the 
surely as does the rosette of 
leaves. At length, a little 
while before the flowers in 
the head blossom, the head 
ceases to turn, but the rosette 
of leaves and the stem also, 
to some extent, continue to 
turn with the sun. When 
the leaves become mature 
and cease growing, they also 
cease to turn. It is not true 
that the fully opened sun- 
flower head turns with the 
sun, as 1s com- 
monly sup- 
posed. But I 
have observed 
young heads 

four to five <(Hq_ 
inches in diameter follow the sun all day. eae 
Fia. 179. Seedling sun- 
The growing end of the stem will also ftower; at left with 
light from above, at 
follow the Sun, even if all the leaves and  yignt turned toward 
indow. 
the young flower head are cut away. ” 
Experiments with sunflowers and other seedlings. 
The 
seedlings of many plants are so sensitive to the 

