LEAF MOSAIC 121 
plane, in such a manner that overlapping is reduced 
to a minimum (Fig. 21). This is well seen in hori- 
zontal branches of the Elm and other familiar trees. 
In the plant chosen for illustration (Azgara micro- 
phylla, a Chilian shrub), an interesting arrangement 
Fic, 21.—AZARA MICROPHYLLA. }, 
obtains. One of the pair of stipules which subtends 
each leaf is itself leaf-like, and stands at an angle, so 
that a mosaic is formed of true leaves (the larger ones) 
and stipules (the smaller alternating ones). On all 
stems the leaves are arranged not at haphazard, 
but according to definite rules. Sometimes they 
