FOREST TREES OF THE PACIFIC SLOPE. 323 



through forests of other trees or in the open. Their habitat includes wet, 

 swampy, moist, rich soils as well as the driest and most arid ones, but all grow 

 at low elevations. 



A single group only of this family, the hackberries. is represented in the 

 Pacific region, where its representatives arc rare. Other North American trees 

 of this family belong to eastern United States. 



CELTIS. HACKBERRIES. 



A small group of large or medium-sized trees and shrubs, represented in the 

 Pacific region by two species. The rough bark is characteristically marked by 

 projecting, knife-like ridges, and the light-colored wood is distinguished by the 

 zig-zag lines of fine pores which mark each layer. Peculiarities of the leaves 

 are their unequal sides, their conspicuously 3-nerved or veined bases, and their 

 arrangement on the twigs so as to form flat sprays, which makes them appear 

 to grow alternately from two opposite sides of the branchlets. 



The minute, inconspicuous flowers (comprising those of male sex, and those 

 which combine male and female organs — perfect flowers) are produced in spring 

 on new twigs of the year, male flowers at the base of the twig and the perfect 

 ones singly, usually on thread-like stems springing from the bases of the leaves 

 at the end of the branchlet. Perfect flowers develop into single cherry-like 

 fruits, which have a thin, dry, sweetish flesh covering a very hard-shelled, 

 smooth or roughish seed. The seeds are rather difficult to germinate, being 

 apt to "lie over" for a season before they grow, unless planted or falling in a 

 soil that is constantly moist. 



Wood of the hackberries is commercially of only secondary importance at 

 present ; that of the two species occurring in the Pacific region is of no value 

 there, but one of these trees produces useful timber in eastern forests. 



Hackberries are of ancient origin. Remains of those from which European 

 species descended have been discovered in the Miocene formation of that 

 continent. 



Hackberry. 



Celtis occidenialis a Linnanis. 

 DISTINGUISHING CHARACTERISTICS. 



Hackberry is rare, and only a small tree or low shrub, generally under 25 feet 

 in height and 10 inches in diameter in the Pacific region. East of the Rocky 

 Mountains, its principal range, it is a straight, slim tree from 80 to 90 feet high 

 and from 2 to 3 feet through when grown in the forest; in the open it has a 

 shorter and, often, thicker trunk, and a very broad, symmetrical, rounded crown 

 of large limbs, which are intricately branched and sometimes drooping. The 

 trunks and limits are grayish in open situations, and apt to be brownish gray 

 in shaded places, and are conspicuously marked with irregularly shaped pro- 

 jecting ridges of bark. Young twigs are pale green, but at the end of the sea- 

 son they are clear reddish brown, with minute, flat, pointed buds, peculiarly 

 dark chestnut. What appears to be a terminal winter bud is the last side, or 

 lateral, bud, at which the immature terminal part of the twig has broken off. 



"A number of varieties, and even species, Jiave been distinguished, based mainly upon 

 the size, texture, and teeth of the leaves, as well as upon the color and size of the 

 "berries." These forms, the validity of which is in doubt, occur mainly, if not entirely, 

 east of the 100th meridian. They will be considered in Parts II and III of this work, 

 which deal with trees east of the Pacific region. 



