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 Pig. 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 .Bwcfe, — G-enerally 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 tMs case stipules, § 117. 



