STREET TREES. 25 



The sugar gum ^ is ji drought-resistant variety, but it does not 

 withstand cold. It is a common roadside tree in southern California, 

 but becomes straggling with age. 



GINKGO. 



The ginkgo, 2 or maidenhair tree (fig. 4, 5), is a native of Japan that 

 thrives in a cool climate or a hot, moist one and succeeds in regions 

 ] , 9, 10, 11, 12, and 13. It is 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 

 slight rainfall. It is 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 elmi. 



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 Eucahjptiis corynocalyx F. Muell. ^ Celtis occidcntiUs L. 



2 Ginkgo biloba L. ^Celtis mississippiensls Bosc. 



137389°— 19— Bull. 81G 4 



