STEMS AND BRANCHES lo 
of very irregular growth is the Catalpa (Indian Bean), 
shown in Fig. 4. The tendency to grow irregularly 
usually increases with age. The Buttonwood, for ex- 
ample, grows quite regu- : 
larly until it reaches the ae 
age of thirty to forty ~.2ick 
years; then its new = 
branches grow in pecu- 
liarly irregular ways. 
The twigs of a very old 
and a young Apple-tree 
illustrate this change 
which age produces. — 
There are great differ- 
ences in the color and 
surface of the bark of 
the twigs of different 
species of trees; some 
are green (Sassafras), Fig. +. 
some red (Peach, on the sunny side), some purple (Cherry). 
Some are smooth and dotless, some marked with dots 
(Birch), some roughened with corky ridges (Sweet 
Gum), ete. 
The taste and odor of the bark are characteristics 
worthy of notice: the strong, fragrant odor of the Spice- 
bush; the fetid odor of the Papaw; the aromatic taste of 
the Sweet Birch; the bitter taste of the Peach; the mu- 
cilaginous Slippery Elm; the strong-scented, resinous, 
aromatic Walnut, ete. 
The branches of trees vary greatly in the thickness 
of their tips and in their tendency to grow erect, hori- 
zontal, or drooping. Thus the delicate spray of the 
Birches contrasted with the stout twigs of the Ailanthus, 
or the drooping twigs of the Weeping Willow with the 
erect growth of the Lombardy Poplar, give contrasts of 
the strongest character. In the same way, the direc- 
tions the main branches take in their growth from the 
