Moore : The study of winter buds 



133 



of the leaf is only the last phase of a long-continued development 

 whose stages of progress can be little known without a micro- 

 scopic study of the internal structures and tissues. 



Microscopic study of growth 



It is not the purpose of this investigation to trace the growth 

 and development of leaves or leaf tissues from a purely embryo- 

 logical or cytological standpoint, but to consider changes in the 

 size of cells already present, the addition of new cells or tissues, 

 and the organization of new leaf fundaments. 



A microscopic study of buds taken from the somewhat miscel- 

 laneous collection of trees and shrubs previously mentioned re- 

 veals a wide variability in the stage of development at which the 



mm. 



Figure F. Hicotia microcarpa. Curves of growth of the buds in length and 



diameter. 



leaf buds enter the winter rest. At one extreme stand Fagns 

 americana and Fagus sylvatica with all of their leaves well formed 

 and the future terminal and axillary buds present and in an ad- 

 vanced stage of development. At the other extreme stand Betnla 



