. Foundations of botany. ig. 87,1. —Types of , 2, Cherry ; 3, 4, European walnut; 5, 6, snowball; 7, ladys mantle ; 8, oxalis. is folded smoothly, and then the three leaflets packedclosely side by side. All these modes of vernation andmany others have received accurate descriptive names b^-which they are known to botanists. 137. Importance of Vernation. —The significance of ver-nation is best understood by considering that there are two BUDS 127 important purposes to be served ; the leaves must bestowed as closely as possible in the bud, and upon begin-ning to open they must be prot
. Foundations of botany. ig. 87,1. —Types of , 2, Cherry ; 3, 4, European walnut; 5, 6, snowball; 7, ladys mantle ; 8, oxalis. is folded smoothly, and then the three leaflets packedclosely side by side. All these modes of vernation andmany others have received accurate descriptive names b^-which they are known to botanists. 137. Importance of Vernation. —The significance of ver-nation is best understood by considering that there are two BUDS 127 important purposes to be served ; the leaves must bestowed as closely as possible in the bud, and upon begin-ning to open they must be protected from too great heatand dryness until they have reached a certain degree offirmness. It may be inferred from Fig. 87, I, that it iscommon for very young leaves to stand vertically. Thisprotects them considerably from the scorching effect of thesun 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, II. — Development of an Oxalis Leaf. A, full-grown leaf; B, rudimentary leaf, the leaflets not yet evident; C, moreadvanced stage, the leaflets appearing ; D, a still more advanced stage ;£, C, and Z), considerably magnified. tected from the attacks of small insects by a coating ofwool or down, which they afterwards lose. Those of thetulip tree are enclosed for a little time in thin pouches,which serve as bud-scales, and thus entirely shielded fromdirect contact with the outside air (see Sect. 117). 138. Dormant Buds. — Generally some of the buds on abranch remain undeveloped in the spring, when the otherbuds are beginning to grow, and this inactive conditionmay last for many seasons. Finally the bud may die, orsome injury to the tree may destroy so many other budsas to leave the dormant ones an extra supply of food, and 128 FOUNDATIONS OF BOTANY this, with other causes, may force them to develop and togrow into branches. Sometimes the tree altog
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