FOLIAGE. 



149 



colouring substance called anthocyanin, which (Overton) 

 may be produced directly by exposing leaves to sun 

 at a temperature of i6°-2 2° C. 



(4) There may be a gummy, varnished, or oily 

 covering. 



(5) They may be enclosed in an armour of over- 

 lapping scales, which are themselves leaves, or parts of 

 leaves, modified to protect the bud. 



Fig. 18. — Developing Leaves. (1-4) Buttercup (Ranunculus repens) : (3) 

 shows the edge of a very minute bud leaf scarcely free from the sheath of the 

 older one 2 ; the leaf at i is about to expand into the normal mature position seen 

 at 4. (5) Azalea showing the erect, hairy and folded bud leaves. 



(6) Small hard tips occur on the teeth of the leaves, 

 and, when young, guard the tissues below and between 

 them. 



Many botanical names are given to the ways in 

 which the young leaves are rolled or plaited. Amongst 

 the neatest and best arrangements are the following : 

 The Lily of the Nile {Richardia Ethiopica) — not a Lily, 

 but belonging to Araceae — has at the base of every leaf 

 a little hollow sheath or tube. The young leaf is rolled 

 up like a scroll of paper, and fits into this hollow 



