STUDIES OF TREES IN WINTER 



lenticels, they are openings for admitting air 

 to the inner tissues. Lenticels are conspicu- 

 ous in the bark of the birches. 



The presence of thorns on the trunk and 

 branches of certain trees helps us to distin- 

 guish them from others, and the clusters of 

 dry fruit which remain hanging on some trees 

 through the winter are another means of iden- 

 tification. 



Stems and Stems and twigs vary from the 

 Twigs finest, lightest sprays to the most 

 coarsely moulded ones, — from the delicate twigs 

 of the hop hornbeam to the stout shoots of 

 the horsechestnut ; — like larger branches their 

 tips either ascend, droop, or grow at right 

 angles from the stem, and may be smooth, 

 downy, or rough to the touch. 



The pith in cross sections of twigs shows 

 different forms and is a means in itself of dis- 

 tinguishing some trees. It is usually circular, 

 but in some species it takes the form of a' 

 pentagon or a star. In a vertical section we 

 sometimes find it in horizontal plates, like the 

 chambered pith of the walnuts. The color is 

 usually white, but sometimes we find it pink, 

 yellowish, green, red, and brown. 



It is interesting to find that the history of a 

 tree for several years past can be told by study- 



