THE WORK OF STEMS 251 



beginning to show a differentiation into blade and 

 stalk. A little lower down the thin blade {hi) of 

 the leaf is seen, crumpled in a wavy manner between 

 the successive thickened veins. In the axil of each 

 leaf is a tiny bud, a miniature of the larger one in 

 which they are contained. Notice that the fibrous 

 bundles (/',/") extend almost to the tip of the stem and 

 send off branches to each leaf and each bud. You can 

 trace their course clearly by placing the cut end for a 

 a time in eosin solution. 



Notice how the overlapping of the older leaves pro- 

 tects the younger ones. Protection from drying is very 

 necessary, for the younger leaves are exceedingly sen- 

 sitive. Remove most of the outer leaves and note the 

 effect on those which remain. 



Remove the bud -scales from winter -buds, and 

 note the effect. The water -proof varnishes of such 

 bud - scales are an excellent protection against drying 

 (the popular notion that bud -scales protect against 

 cold is a fallacy) ; see also pages 213 and 21-1. 



The protection of the tip of the stem by the over- 

 lapping bud- scales and young leaves is due to the fact 

 that these organs grow faster on the lower side than 

 on the upper, thus causing them to curve inward. 

 When the bud opens, the reverse process occurs, 

 growth becoming more rapid on the upper side. In 

 some leaves this condition persists, giving them a per- 

 manently curved appearance or causing them to flatten 



