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STREET TREES. 25 
The sugar gum! is a drought-resistant variety, but it does not 
withstand cold. Itis a common roadside tree in southern California, 
but becomes straggling with age. 
GINKGO. 
The ginkgo,? or maidenhair tree (fig. 4, B), is a native of Japan that 
thrives in a cool climate or a hot, moist one and succeeds in regions 
1,9, 10, 11,12, and13. Itis extremely erratic in its behavior, some- 
times growing well, sometimes practically not growing at all, but 
where it succeeds it is very disease resistant, and it withstands 
severe windstorms remarkably well. The leaf is peculiar in appear- 
ance, resembling in outline a much enlarged leaflet of maidenhair 
fern with a corrugated surface. The tree is conical when young, but 
as it reaches maturity its top usually fills out, making a broad, almost 
flat-topped, handsome tree. Only the staminate form should be 
used, because the pistillate form bears fruits the flesh of which is 
slippery and dangerous when it drops to the pavement, and to some 
people it is somewhat poisonous to the touch. Ginkgo trees, there- 
‘fore, would need to be secured by budding or grafting from the 
mature staminate form. 
HACKBERRIES. 
The hackberry,? or sugarberry; is especially valuable in regions 
6, 7, 8, and 9, as it grows satisfactorily where there is comparatively 
sheht rainfall. Itis also much used in region 11, but should be super- 
seded there by other varieties that are better. It is of moderate size 
with an oblong head and of rather open growth. It is comparatively 
short lived. Its leaves are much like those of the elm. : 
The name sugarberry comes from the sweet black berries that are 
borne in the early fall. The tree is sometimes affected by a fungous 
trouble known as witches’-broom. This trouble causes large numbers 
of small sprouts to start from the affected portion, which gives the 
infected tree an unsightly appearance. The hackberry should not 
be planted where this trouble is prevalent. 
‘The Mississippi hackberry‘ is a large, open, oblong-headed tree 
with smoother leaves than the common hackberry. It is useful in 
the southern part of region 6, in region 8, and to some extent in regions 
11 and 12. It thrives well under the same adverse moisture condi- 
tions as the common hackberry. The trunk and the large branches 
have little wartlike projections of the bark scattered irregularly over 
them. The small twigs are sometimes more or less spotted or winged 
in the same way. ‘The tree is rather larger than the common hack- 
berry and apparently is less subject to witches’-broom. 
1 Pucalyptus corynocalyr F. Muell. 3 Celtis occidentalis L. 
2 Ginkgo biloba L. {Celtis mississippiensis Bose. 
137389°—19— Bull. 816——4 
