94 ESSENTIALS OF BOTANY 
each half of the leaf is plaited in a somewhat fan-like 
manner, and the edges of the two halves are then brought 
round so as to meet; in the lady’s mantle the fan-like 
plaiting is very distinct; in the wood sorrel each leaflet 
is folded smoothly, and then the three leaflets are packed 
closely side by side. All these modes of vernation and 
many others have received accurate descriptive names by 
which they are known to botanists. : 
111. Importance of Vernation. — The significance of ver- 
nation is best understood by considering that there are 
two important purposes to be served: the leaves must be 
Fic. 57. Development of an Oxalis Leaf. 
A, full-grown leaf; B, rudimentary leaf, the leaflets not yet evident; 
C, more advanced stage, the leaflets appearing; D, a still more 
advanced stage. (B, C, and D considerably magnified.) 
stowed as closely as possible in the bud, and upon begin- 
ning to open they must be protected from too great heat 
and dryness until they have reached a certain degree of 
firmness. It may be inferred from Fig. 56 that it is 
common for very young leaves to stand vertically. This 
protects them considerably from the scorching effect of the 
sun at the hottest part of the day. Many young leaves, 
as, for instance, those of the silver-leafed poplar, the pear, 
the beech, and the mountain ash, are sheltered and pro- 
tected from the attacks of small insects by a coating of 
