VERNATION 



85 



99. Vernation. The arrangement of leaves in the bud is called 

 vernation ; some of the principal modes are shown in Fig. 86. 

 In the cherry the two halves of the leaf are folded together flat, 

 with 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 snow- 

 ball 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 vernation, and ax 

 many others, often characteristic 

 t)f groups of plants, have received 

 descriptive names by which they 

 are known to botanists. 



100. Importance of verna- 

 tion. 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. 86 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 cold, dryness, and the attacks of small 



FIG. 85 



S, a twig of European elm; A, a 

 longitudinal section of the buds of 

 B (considerably magnified) ; ax, the 

 axis of the bud, which will elongate 

 into a shoot ; sc, leaf scars. After 

 Behrens 



