BUDS L2¢ 
important purposes to be served; the leaves must be 
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. 87, I, 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- 
Fig. 87, Il: — Development of an Oxalis Leaf. 
A, full-grown leaf; B, rudimentary leaf, the leaflets not yet evident ; C, more 
advanced PRES the leaflets appearing ; D, a still more advanced stage ; 
B, C, and D, considerably magnified. 
tected from ie 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 thin pouches, 
which serve as bud-scales, and thus entirely shielded from 
direct contact with the outside air (see Sect. 117). 
138. 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 food, and 
