330 THE WOODY STEM 



They can be distinguished from the " leaf buds " (buds 

 of shoots which will produce leaves, but no flowers) at 

 any time during the winter in such fruit trees as the 

 pear, and very easily in early spring when they have 

 begun to sweU, by their more rounded form. 



In the spring the tissue of the axis begiiis to grow, 

 and this growth eventually bursts the] bud and pushes 

 out the foliage leaves, which unfold and grow to their 

 full size, while the internodes of the stem elongate. 

 If there are young flowers in the bud, these also grow 

 and open. The winter bud scales fall off, leaving a 

 zone of scars on the stem, and these will clearly mark 

 the junction of last year's stem and the stem formed 

 during the present growing season. At the close of 

 the growing season the fohage leaves fall off, and the 

 terminal bud (or sometimes a lateral which takes the 

 place of the terminal) once more passes into the winter 

 condition by forming winter bud scales which close it 

 in. These again wiU fall off and leave another zone of 

 scars in the next spring. In this way successive zones of 

 bud scale scars are left on the stem, and the interval 

 between two of these zones represents a year's growth 

 of the branch. By noting the positions of these zones 

 the history of a woody branch can be read for some years 

 back. Eventually the scars are destroyed by the scahng 

 off of the bark. 



Some of the axillary buds formed on the current 

 year's shoot may grow out during the growing season 

 to form branches. The rest form winter buds, and of 

 these some will grow out next spring, but others 

 remain small {dormant buds), and will only grow out later 

 on, under some special stimulus, such as may result, for 

 instance, from the destruction of the terminal shoot. 



Secondary Meristems. — Growth in thickness of a 



