802 —C«; THE UNFOLDING OF WOOD-SORREL LEAVES. 
noticed them at all will remember their shape—a trefoil with 
little notches in the middle of each division. The mature leaf is 
flat, the leaflets being set at right angles to the stalk. But how 
did the leaf grow like this? or did it grow out of the ground in 
exactly this form and shape? This latter alternative would be 
well-nigh an impossibility, for then the leaf would offer a large 
plane of resistance to the overlying soil. As a matter of fact, it 
1 2 3 4 4a 5 6 
In the next stage the leaf is beginning to open, and here the three 
leaflets may be distinguished. They are in fig. 2) all folded 
at the same time they open slightly, as shown in fig. 4. In igs. 
5 and 6 further positions may be traced; the middle leaflet, having 
e unfolding completely, until 
they form the flat, three-divisioned leaf which we set out from. 
9 
In this way the middle leaflet not only revolves through about 
t -fourths of a circle, but afterwards reverses its motion, until 
it is about at right iigtee to the stalk; and during all this compli- 
cated moti : i . i ; 
but it is very easy to trace it in nature, and in early spring 
found in almost all stages, growing close to each 
