148 TLANT LIFE. 



excellent example of this. (The so-called " Oak " 

 which one sees on cutting across the base of the 

 leaf-stalk is the mechanical tissue.) Besides the 

 supporting veins springing from the mid-rib or stalk, 

 the lateral connecting nerves which hold these together 

 are often of mechanical importance, as may be seen, for 

 example, in the blackberry leaf These, like the rim 

 or hem on the holly leaf edge, diminish the tearing 

 effect of the wind. 



The shining glossy character of many leaves is 

 supposed to be of some importance. In tropical 

 climates, where there are very heavy rains and where 

 the leaves of plants are subject to attacks from parasitic 

 Algae or encrusting Licliens, it is of great importance 

 that the leaf should dry rapidly. Moisture upon it 

 favours the development of these enemies, and also the 

 growth of fungus spores. It is found that in such 

 climates a large proportion of the plants have leaves of 

 a glossy character ; and it is very probably the case, 

 that the moisture dries more quickly on such glossy 

 leaves. 



The protection of leaves during their young and 

 tender bud condition is, of course, very necessary. All 

 sorts of mites, beetles, and other insects, are apt to 

 attack the buds ; and, besides these enemies, the young 

 leaf has to be protected against changes of temperature, 

 and especially against the loss of water in dry weather. 

 Before the leaves take their final position as mature 

 workers in the general economy, they are protected in 

 all sorts of ways, of which the following are amongst 

 the most easily observed. They may be : 



(i) Rolled up or folded together in the bud. 



(2) Covered with closely set silky or woolly hairs. 



(3) They may have a red colour, due to a special 



