BUDS. 83 
the under surfaces outward; in the walnut the separate 
leaflets, or parts of the leaf, are folded flat and then grouped 
into a sort of cone ; in the snowball 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 packed closely side by side. All these modes of ver- 
nation and many others have received accurate descriptive 
names by which they are known to botanists. 
-111. Importance of Vernation.— The significance of verna- 
tion is best understood by considering that there are two 
important purposes to be served; the leaves must be stowed 
as closely as possible in the bud, and upon beginning 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. 61 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 protected from the attacks of small insects by a coating 
of wool or down, which they afterwards lose. Those of the 
tulip tree are enclosed for a little time in a thin pouch, 
formed from the bud-scales,? and thus entirely shielded from 
direct contact with the outside air. 
112. Dormant Buds. — Generally some of the buds on a 
branch remain undeveloped in the spring, when the other buds 
are beginning to grow, and this inactive condition may last for 
many seasons. Finally the bud may die, or some injury to the 
tree may destroy so many other buds as to leave the dormant 
ones an extra supply of nourishment, and this, with other 
causes, may force them to develop and to grow into branches. 
1 These are in this case stipules, § 117. 
