FOREST TREES OF THE PACIFIC SLOPE. 429 



The flowers (usually bisexual), appearing In spring with the leaves, differ 

 from those of other Pacific ashes in having their parts white and showy, as in 

 ordinary plant blossoms (fig. 204, a). The conspicuous part of the flowers is, 

 as the technical name indicates, of two white divisions (petals). Twigs of a 

 season's growth are more or less distinctly 4-angled and smooth. Mature leaves 

 are smooth throughout, with from 5 to 9 (sometimes 3) thick leaflets (fig. 204). 

 Mature fruit (fig. 2<i4), variable in the length of its wings, is ripened in late 

 summer. 



Upon the occasional occurrence of individuals with leaves of 3 leaflets is 

 based the variety Fraxinus dipetula trifoliolata Torrey, while F. dipetala 

 brachyptera Gray is based on exceptionally short fruit I one-half to three-fourths 

 inch long), the wiug being about one-half as long as the body of the seed. 



California. — Along streams of the inner coast ranges and foothills of the Sierra 

 Nevada. 



OCCURRENCE. 



On borders and in vicinity of foothill streams and in gulches ; in dryish or slightly 

 moist rocky and gravelly soils. In clumps and mingled with chaparral. 



Family BIGNONIACE^. 



Bignoniaeere is a large group popularly known as the bignonia or trumpet- 

 vine family. It contains such popular climbing shrubs as the trumpet- 

 vine and the well-known catalpas — so valuable for their quickly grown, durable 

 wood. Representatives of the family are particularly numerous in the tropical 

 regions of the western hemisphere. The family comprises nearly 100 genera, 5 

 of which occur in the United States, while 3 of these, Crescent hi, Catalpa, and 

 Chilopsis, are groups of trees: the latter genus only is represented in the Pacific 

 region. The flowers are large and showy, trumpet-like, or funnel-shaped, and 

 the leaves of all (except Crescentia i are alike in being arranged on the twigs in 

 pairs. The fruits (except in Crescentia) are long pods which split in half and 

 have very light, flat, often fringed seeds, with two delicate wings. 



CHILOPSIS. 



This genus contains but one species, and its characters are included in the 

 following description of its representative. 



Desert Willow. 

 Chilopsis linearis (Cav.) Sweet. 



DISTINGUISHING CHARACTERISTICS. 



Desert willow is little known except to those who travel in its arid range, 

 where it is called "desert willow" because of its narrow, willow-like leaves. 



Ordinarily from 10 to 20 feet high, with a narrow crown of slim, upright 

 branches, and a short, often crooked or leaning trunk from 2 to 6 inches through; 

 sometimes larger ; very often shrubby, with several or many slender stems from 

 5 to G feet high. Bark of even the smaller stems is regularly cut by seams into 

 a network of deep yellowish-brown, shallow, connected ridges. Twigs of a sea- 

 son's growth are smooth (sticky or densely woolly at first), and pale yellowish 

 to reddish brown. Mature leaves (fig. 205), which persist from spring until 

 15188— OS 28 



