STEMS, THEIR FORMS AND FUNCTIONS 73 



sudden changes of temperature. The leaves themselves are 

 wonderfully well packed, so as to expose little surface, and econo- 

 mize space; they may be folded, rolled, or coiled, but always 

 in the same way in the same plant. 



Buds are always developed either at the end of the stem 

 (terminal), or just above the leaves (lateral). Their growth 

 consists of three stages, the opening of the scales, the lengthening 

 of the stem, and the expansion of the leaves. The scales fall off 

 during this process, leaving the bud-scale scars to mark their 

 former place. As most buds begin growth in the spring, these 

 rings of scars mark the beginning of each year's growth. The 

 age of the stem can thus be calculated as long as the scars show. 



SUMMARY 

 Definition. 

 Characteristics of stem 



Bears leaves, flowers, fruit. 



Leaves and branches at nodes. 



Growth between nodes. 

 Functions : 



{of leaves for light and air. 

 of flowers for pollenation. 

 of fruits for dispersal. 



Transportation of liquids between root and leaf 

 Storage of food. 

 Propagation. 



Kinds of Branching: 



Object of branch arrangement in general. 

 Branching due to leaf arrangement. 



Opposite. (Ex.) 



Alternate. (Ex.) 

 Branching due to bud development. 



1. Excurrent. (Ex.) 



Shape of tree. Cause. 

 Advantages: 



Rapid growth in height. 



Little storm resistance. 



Can grow closely. 



Shed snow readily. 



2. Deliquescent. (Ex.) 



Shape of tree. Cause. 

 Advantages, shades out its neighbors. 

 Few can grow together. 



