EXERCISE 32 



PREPARATION FOR NEW GROWTH IN THE STRUCTURE 

 OF THE BUD 



Materials. Twigs and buds as in preceding exercise. 



Directions for work. Examine a scaly bud in its winter con- 

 dition to discover what indications of next spring's growth may 

 be found in autumn and how the growing point is protected 

 during the winter. 



Pick off the scales one by one, with care to remove the entire 

 scale in each case. Note differences in the scales as you reach 

 the deeper parts of the bud. When the last of the bud scales 

 has been removed, note the central part of the bud, which 

 represents the preparation for next year's growth. Can you 

 distinguish leaves ? If so, count them. Can you find a stem ? 

 Examine with a hand magnifier to make sure on the above 

 points. If leaves are found, distributed along a short stem, this 

 constitutes a miniature leafy shoot. What changes would need 

 to take place in the spring to transform the contents of the bud 

 into a shoot capable of making food? 



Examine another bud with reference to the protection of the 

 growing point from the unfavorable conditions of winter. Com- 

 pare with a longitudinal section through a bud (Exercise 31). 

 About what is the thickness of the protective layer of bud 

 scales ? Do they fit closely or loosely ? Would this thickness 

 be sufficient, in your opinion, to keep the center of the bud 

 above freezing temperature during a long period of zero weather? 

 If possible to do so, cut open buds out of doors in severe weather 

 and note whether the interiors of these buds appear to have 

 escaped freezing. Would the bud covering be effective in 

 delaying freezing and thawing ? 



Consider the need of ' protection from drying. Is it probable 

 that water would evaporate from an unprotected growing point 

 during cold weather ? Does water evaporate from other objects, 

 as from wet clothing, while frozen ? Does it seem probable that 

 water would be supplied to the bud by ascending through the 

 stem during very cold weather ? Why ? Is the layer of scales 



[37] 



