CHAPTER IX. 



THE OPENING OF THE BUD AND EXTENSION OF 

 THE SHOOT. 



"Swelling" and "bursting" of the bud Due to thrusts of expanding 

 leaves Vertical section of bud The same after extension 

 Further development of shoot The winter state True ter- 

 minal buds Aborted buds Shoots and Twigs Annual growth 

 of shoot Leader Periodic growth Maximum extension 

 Variations in growth Secondary growth "Lammas shoots." 



WHEN the bud " swells " and " bursts " in spring, two 

 principal actions are at work, though both are due to one 

 fundamental property of the young organs. 



The first of the two actions referred to is the upward 

 thrust of the growing apex of the shoot as it elongates. 

 This process has often been compared to the extension 

 of a telescope, as the segments are pulled out, and the 

 illustration is apt in so far that the bud-axis does grow 

 especially at the internodes between the nodes, thus 

 driving the leaves or pairs of leaves further apart, but it 

 is a far more complex process than the illustration of 

 the telescope would suggest, and the analogy must not 

 be pushed far. The most essential distinction is that 

 in extension by growth there is ultimately an addition of 

 material, brick on brick as it were, to the substance of 

 the segments. 



